BOTANICAL RESEARCH AT THE ACADEMY
The Natural History of Plants:
The Academy was the realization of the House of Solomon, an instrument of royal propaganda, the hub of a sociopolitical network of influence. But it was more. It was a catalyst for thought whose facilities, customs, and corporate self-consciousness influenced the work its members performed. The institution cannot be understood apart from its scientific research and writings, for these were its ostensible raison d'être. Whatever other functions the Academy had, a satisfactory scientific performance was a necessary condition for its survival.
The Academy's interests are so broad as to elude detailed analysis in any one study. Concentrating on a single facet of its research, however, clarifies both the discipline and the institution. Botany offers a particularly rewarding case, for under the influence of chemistry, microscopy, anatomy, and physiology, it was changing. By academicians' own standards, moreover, much of their botanical research was a failure, and the historian can often learn more from failures than from successes. Since some of the Academy's work on plants attracted the concern of its protectors, it clarifies the direct and the indirect effects of patronage. Finally, with respect to organization of research and modes of reasoning, studies of plants resemble other projects at the Academy and thus offer a key to the institution as a whole.
Changing Ways of Thinking About Plants
Academicians thought of research on plants as being of two types: descriptive natural history (l'histoire ), which will be discussed in chapters 6
through 8, and explanatory natural philosophy (la physique ), which will be discussed in chapters 9 through 12.
The concept of natural history goes back at least to Aristotle, whose Historia animalium lays out what its author knows about animals, organizing that knowledge into such categories as number and type of limbs, mechanisms for eating, and mode of reproduction. Aristotle offers a series of generalizations, each modified by exceptions and strengthened by comparisons. Subsequent natural histories always contained these two elements: they enumerated the pertinent facts and they generalized in order to organize the facts. Aristotle's book introduced his treatises on the functions of the various parts of the body, reproduction and generation, and other aspects of a natural philosophy of animals. It was the necessary preliminary to causal analysis. But the blend of assumption and generalization in Aristotle's work, as in the natural histories of later authors, betrays a pattern of causal thought embedded in the method itself.
Surveying the two-thousand-year-old tradition of natural histories, Bacon tried to clarify their uses and limits. Perhaps in revulsion against the magical or superstitious element found in many of them, he declared that a good natural history should present fact shorn of explanation. A natural history of the world would enumerate all observable phenomena, category by category (for example, winds, heat and cold, plants, animals, and minerals). Only when savants had compiled this information could they ascertain the underlying causes of phenomena, that is, examine the natural philosophy of the world. Given the immensity of the first task, an ideal Baconian approach would make it difficult ever to reach the second stage.
Some natural histories, consistent with Bacon's recommendation, did little more than illustrate and describe flora and fauna without explaining their behavior or nature. Bauhin's Pinax, for example, the most comprehensive seventeenth-century guide to plants, described the external appearance, cultivation, and uses of each plant. Zoologists, tempted by analogies between human and animal behavior and impressed by the lessons of comparative anatomy, went further. In his ornithology, for example, Aldrovandi not only portrayed the skeletal structure and reproductive organs of birds but also discussed the development of the chick in the egg, the roles of male and female in reproduction, and the sexual mores of fowls. For Aldrovandi, knowing animals entailed knowing their anatomy and physiology and explaining their behavioral characteristics. Aldrovandi's and Bauhin's different methods show how the natural histories of plants and animals diverged at the beginning of the seventeenth century. Zoological research was prompted primarily by comparative anatomy,
while the principal incentive to study plants was pharmacological, so that books on plants tended to be practical manuals.
In the course of the century, however, several influences altered ideas about how to study plants. The conceptions of natural history and natural philosophy changed, bringing botanical and zoological research closer in intent and method. First, the number of known plants grew quickly, making new compendia necessary. Second, among the species discovered in the new world were sensitive plants (fig. 1), which challenged the old Aristotelian distinction between plants and animals, for they moved when touched. Third, aesthetic appreciation of plants and gardens as objects of beauty was developing, and with it a desire to collect botanical illustrations. Insofar as this change represented a taste for plants on their own merits — and not as symbols or simples — it also represented a new way of thinking about plants that would affect botanical studies. Fourth, by redefining the differences between humans and animals, mechanistic theories created a greater incentive to test assumptions about plants and animals — especially the view that plants and animals were analogous in many respects — by searching for the limits of their similarities. Fifth, savants tried to put their causal accounts of the universe on a new footing. Astronomers sought a new celestial mechanics and developed a mathematical key to the language of the universe, while students of terrestrial phenomena turned to chemical and mechanical explanation to account for animal and vegetable processes. Sixth, as new scientific fields emerged and the interdisciplinary character of scientific inquiry was placed on a firmer footing, traditional fields were redefined and theories or methods that developed in one area were applied to another.
All of these factors influenced botanical research, which emerged in the late seventeenth century as a more independent field of study. From the appearance of Bauhin's work until the 1660s, no major treatises on plants had appeared. But during the 1660s Robert Hooke included plants in his Micrographia, Johann Daniel Major suggested that sap circulated in plants like blood in animals, and Robert Morison and John Ray began a new assault on the problem of classification. By the 1670s Nehemiah Grew was publishing anatomical studies of roots and stems, and Marcello Malpighi took up these inquiries in the 1680s.
The Academy was thus founded at a time when botanical research was in flux, exhibiting at once conservative and innovative elements. The Academy's own projects reflect both tendencies. Academicians settled quickly on publishing a definitive natural history of plants, to be produced as a team effort. This study was old-fashioned and stressed descriptions,
lists of synonyms and sources, explanations of medical uses, tips on cultivation, and illustrations, all reminiscent of Bauhin. At the same time, however, academicians introduced new elements such as the chemical analysis of plants. The blend of old and new features, the research methods chosen, and the roles of the patrons and of the institution all contribute to the story of the Academy's natural history of plants. By and large, that story is one of failure. Academicians recorded hundreds of pages of botanical notes and compiled more than twenty volumes of notebooks from chemical experiments. They drafted assorted chapters, prepared more than three hundred engravings, and wrote several books. But they never published the natural history as planned.
The Academy's natural history of plants failed for four reasons: intellectual, natural, accidental, and institutional. The project was intellectually ambitious, its scope and style innovative but overly inclusive. Academicians never focused their inquiry adequately but studied plants rare and common, medicinal and edible, French and foreign. They disagreed about how to describe plants — where to start, what to emphasize, and how to balance bookishness and observation — and they were sometimes undecided whether a specimen corresponded with a plant already described in the literature. Natural obstacles, such as obtaining and cultivating uncommon plants, also taxed their ingenuity. Since they did not keep a herbarium of dried specimens, they could not always check their descriptions or illustrations. Such intellectual and natural problems were not peculiar, however, to academicians. Anyone writing a natural history of plants faced these difficulties, and academicians' solutions and mistakes resembled those of their contemporaries.
The Academy's project was distinctive in certain respects. It was to include chemical analyses of the plants. It was the work of an institution, not an individual. It suffered from editorial rivalry, uncertain funding, and theft. The patronage that made the project possible also undermined its completion. These special features of the project contributed to its failure. Academicians were able to isolate the most treacherous intellectual problem — chemical analysis — from the project, but they could not prevent the accidents and institutional problems that damaged their natural history. To understand how all these factors affected the project, it is necessary to know why the Academy decided to prepare a natural history of plants at all, how innovative the project was, what was the institutional character of members' efforts, and how patronage influenced their work.
Proposals for a Natural History of Plants
Between 1550 and 1700, the number of known plants quadrupled while the number of botanical compendia declined. If only to take account of discoveries, a new natural history of plants seemed a necessity in the late seventeenth century. In 1674 John Ray pointed out the absence of a "general History of Plants." He complained that in order to have the available botanical lore in a single work, it would be necessary to combine the publications of Bauhin, Columna, Alpin, Cornut, Parkinson, Margrave, Morison, and Boccone. Most of the authors he cited were no longer active. But when Ray wrote, members of the Royal Academy of Sciences in Paris had already committed themselves to just such an undertaking as he described. One of their earliest plans was to publish a general natural history of plants.
Huygens was the first to propose that the Academy publish a natural history. The project he described was Baconian and all-encompassing, intended to investigate weight, heat, cold, light, color, magnetic attraction, the composition of the elements, animal respiration, and growth in metals, plants, and stones. The Academy would assign topics to its members, who would report weekly on their findings. This stilted proposal helped convince Colbert and his advisers to found the Academy, but Huygens's colleagues modified his ideas and adopted two specific projects for the anatomists, botanists, and chemists. These were the natural histories of animals and of plants.
It was Huygens's friend Perrault who suggested in January 1667 that the Academy publish a natural history of plants. Perrault too was influenced by earlier models, especially Bauhin's Pinax, which Nicolas Marchant had already begun to revise. Perrault tried to define the field and to differentiate the kinds of research required for a comprehensive study of plants. He identified two ways of studying plants: "pur Botanique et Risotome" and natural philosophy. The former studied the "histoire" of plants by "botanizing" or "herborizing," that is by collecting plants and roots and studying their external characteristics and medical applications. The latter Perrault defined, in the Theophrastean and Baconian tradition, as the inquiry into the causes of medical properties of plants or of vegetable reproduction and nutrition. For such research he envisaged chemical analysis, microscopic observation of seeds and shoots, tests of theories about propagation and generation, and studies of whether sap circulates like blood.
Perrault's plan of research for the natural history was more bookish than
experimental. It was at once grandiose and modest. The Academy would treat all known plants in a comprehensive publication containing descriptions, illustrations, and a topographical index, but would take its information from existing literature. Because classification was problematic, Perrault proposed that academicians choose an existing system or dispense with one entirely. A catalogue of all known names of plants would be useful, but ancient names and descriptions could not always be correlated with modern plants. The compendium would be illustrated from watercolors painted by Nicolas Robert for the duke of Orléans rather than from life.
Like Huygens, Perrault had a traditional conception of natural history. He referred to the ancients but not to the Americas, and indeed the Academy looked primarily to Europe and the Near East for unusual species, leaving American flora to the Minim Charles Plumier. As a physician, Perrault also stressed the medical merits of the project, urging academicians to correct and expand materia medica. The Academy's task was to collect useful information as efficiently as possible and make it available to the public. This literary approach especially suited a society that had existed formally for only one month, as yet possessed no laboratory and little apparatus, and still used meetings to plan or debate. Perrault was also uncertain about the extent of royal patronage. A modest proposal, firmly rooted in work already begun, stood a chance of succeeding and might stimulate a more broadly conceived project, if only Colbert would authorize it.
By criticizing Robert's paintings, Perrault ultimately justified expanding the Academy's project. He showed that aesthetic criteria did not meet scientific needs. Most of the paintings did not show roots or indicate the relative size of a plant, defects that would trouble a scientist but not a connoisseur. Perrault's remedy was to add the missing roots and to depict leaves, fruits, and seeds in blank corners of the page (fig. 2). Should the Academy be allowed to commission illustrations from life, however, Perrault recommended that the artist portray the plant life-sized or provide a scale and show the important parts of plants; when the appearance of a plant changed markedly as it grew, the artist should depict both the young and the mature plant.
Perrault's colleagues were not content with studying books but wanted to study nature. They would start with the literature and go beyond it. Indeed, since European botanical literature referred to only a small proportion of known plants, the greatest need was to study the new or "rare" plants. Here, too, the Academy was influenced by work begun by Guy de La Brosse and the duke of Orléans, especially since Marchant had worked
for the latter at Blois. But the Academy also added an experimental twist to Perrault's natural history by incorporating chemical analyses designed to explain what they were describing. This was Duclos's contribution to the project.
As director of the project, Duclos quickly put his own stamp on it. To the basic elements — engravings and descriptions of plants — he added a classification according to Theophrastus's system. He also expanded the descriptions to compensate for the faults of the illustrations. Descriptions of the size, parts, and products of plants would form a catalogue of characteristics that would distinguish one plant from another. He stressed for example the "carriage" or appearance (le port ) of the plant in the earth, that is, whether a plant was tall (eslevée ), or rested its branches on the earth without sending out roots from them (couchée ), or rested its branches on the earth and sent out roots from them (rampante ), or leaned (appuyée ). Duclos also demanded precise descriptions of the root, trunk, leaves, flowers, fruits, seeds, and natural products such as gums, resins, or liquids.
In a more radical departure, Duclos added chemical analysis to the work. He planned to distill plants in order to mention in the descriptions the consistency, color, smell, and taste of distillants. He hoped to discover the chemical constitution of plants by analyzing their distillants, by testing a decoction of sap or juice in various solutions, and by studying crystals formed by condensed juices. Because Duclos believed that chemical explanation of organic matter was fundamental, he made chemical analysis an integral part of the natural history of plants. Under the guise of description, therefore, he introduced inquiries that bordered on natural philosophy. In so doing Duclos set the natural history on a new and difficult footing that made the project controversial and delayed its completion.
Duclos also thought the natural history should have a regional bias, focusing on French flora. Thus, he recommended that the common French names be in the list of synonyms of plants:
And because we plan to write this natural history in the French language, it would be good to be informed about the names which the common people in the major French provinces give to each plant, so as to add them to the names used in other languages.
The natural histories of plants and animals, like nearly everything academicians wrote, were published in French. The Academy intended to reach above all a French audience. First and foremost, that meant the king, the ministerial protectors, and the persons to whom they distributed the book, as a group probably unfamiliar with Latin. Duclos's interest in popular
French names for plants was controversial, however, and his proposal allied him with the "moderns" against the "ancients" and with the "realists" against the "purists." The same controversy raged in the Académie française, which ruled out of its dictionary neologisms and technical language, the very vocabulary that Antoine Furetière struggled to learn for his own dictionary. Within the Academy of Sciences Duclos had many allies, for academicians coined words so that they could write about plants in their own language, and in the 1670s French names were added to some of the plates.
Duclos's request that the Academy study only French plants was less palatable, despite its advantages. Valuing experience over authority, Duclos wanted descriptions to reflect direct observation, which was possible only when the plants were near at hand. He believed that the provincial flora of France were insufficiently appreciated in scholarly circles. He wanted the Academy's project to be manageable, and he worried that plant species varied when transplanted. Academicians, however, resisted this restriction. In the late seventeenth century gardeners were proud of the exotic flowers and fruits they could cultivate, and Louis XIV's nurseries and orangerie were famous for defying climate and seasons. Connoisseurs and savants alike wanted to expand their knowledge of flora and fauna, not limit it to what was native to France. Although Duclos's proposal was formally approved, the Academy never stopped cultivating, describing, and illustrating rare plants and never limited its projected book along geographical lines. The resulting lack of focus impeded the project.
The Academy accumulated proposals and smoothed over disagreements. Its corporate procedures and plans grew by accretion and ignored inconsistencies. The successive adoption of Perrault's and Duclos's proposals exhibits this tendency well: in some areas they agreed, in others they disagreed, and the Academy simply glossed over any problems of coherence between them. Where Perrault and Duclos were in harmony, they reflected a centuries-old approach to studying plants, with Perrault emphasizing illustrations, Duclos text, to convey information. Duclos also improved on Perrault, whose language had sometimes been vague. But Duclos wanted the natural history to concentrate on French flora and to include chemical analysis, which Perrault regarded as more appropriate to the natural philosophical studies of plants. In any case, when the Academy formally approved Duclos's recommendations in 1668, a basic framework for the natural history existed. The designers were Huygens, Perrault, and Duclos, but the research and writing were almost entirely the responsibility of Nicolas Marchant and Bourdelin.
Duclos quickly lost control of the project to Dodart, who entered the Academy in 1671. His statement of principles appeared in the Mémoires pour servir à l'histoire des plantes , published in 1676 with Marchant's Descriptions de quelques plantes nouvelles . The books were an inconsistent introduction to the project, for Dodart discussed chemical analyses of plants at length, but Marchant omitted them from his descriptions.
Dodart accepted many of Perrault's and Duclos's criteria for describing plants; he also learned from Marchant's experience of writing descriptions. He reaffirmed that the Academy's goal was to publish a description of every known plant. He agreed with Perrault and Duclos that the function of any description was to enable the reader to distinguish one plant from another. As a result, he limited descriptions to the parts of plants that served this purpose, or that helped to discover the uses of the plant, or that revealed "some particular industry of nature." When its surroundings affected the appearance of a plant, these also were to be indicated. Because the botanical vocabulary of the French language was limited, Dodart warned, academicians would coin words or borrow them from the vernacular.
More important, the Academy was now able to commission its own drawings from life. Many of the illustrations in Marchant's Descriptions de quelques plantes nouvelles were copied from the duke's watercolors. But Dodart's Mémoires des plantes announced that the king's patronage would henceforth suffice to obtain engravings of the highest scientific standard; the Academy's artists would refer to the watercolors only if Marchant could not grow certain rare plants. The Academy would take the utmost pains to obtain accurate and detailed pictures. The engravers drew delicate parts or very small plants with the help of a microscope, and they used etchings (eau forte ) rather than line engravings (taille-douce ) to suggest shades of color (figs. 1-12). Instructions to the artists reflected Perrault's and Duclos's recommendations. Thus, illustrations would indicate the actual or relative size of each plant and portray the appearance of the plant in the earth (figs. 3, 4). They would also include a picture of the young plant, "whenever it first appears in a shape different enough to make it difficult to recognize" (fig. 5).
Familiar with his colleagues' views, Dodart adopted them selectively, usually siding with Perrault. He rejected all known systems of classification, washing the Academy's collective hands of the problem that exercised Morison and Ray and whose solution later brought international fame to Tournefort. Dodart shared Perrault's interest in testing methods of propagating plants and wanted to disprove the Theophrastean claim that plants could be propagated from their saps alone. Both Perrault and Dodart also
hoped the Academy could displace superstitions with observations, in that way teaching the public and raising the standard of knowledge about nature.
Despite such similarities of approach and interest, the Mémoires des plantes was in certain respects Dodart's personal statement about the natural history. First, he affirmed the Baconian principle that one should not "condemn as false something that has not succeeded for oneself, but [instead] simply report the methods and results of one's experiments." Dodart presented the Academy's raw findings, without hypotheses or conclusions. Duclos and Perrault, in contrast, expected the natural history to go beyond mere reports of experiment and difficulty. Second, Dodart introduced plant physiology into the natural history by including an explanation of how a plant grew, perhaps as an analogy with natural histories of animals that reported the development of the chick in the egg. He remained purist enough to exclude nutrition or the movement of sap from the natural history, but the cultivation of plants lent itself to analyses of germination and soils. Whether or not Dodart intentionally challenged traditional definitions, no other academician had included these subjects in the natural history.
In ten years four academicians — Huygens, Perrault, Duclos, and Dodart — designed research on plants. They were inspired by earlier natural histories and by a well-established dichotomy between natural history and natural philosophy. As work began in earnest, old distinctions were eroded and the fate of the project was irremediably altered by the addition of chemical analysis. Before considering the effects of that decision, however, the progress of research in all its aspects — cultivation, description, illustration, and chemical analysis — must be reviewed.
Research for the Natural History
Academicians began work soon after Perrault proposed the natural history, but they needed plants for study. Perrault called for an "Academic Garden" and by the 1670s Nicolas Marchant had commandeered part of the vast and unused territory of the Jardin royal for the Academy. This plot became known as the petit jardin and was formally recognized as belonging to the Academy. In it Marchant and his son cultivated seeds from all over the world, collected by friends, acquaintances, and colleagues.
After cultivating a plant, the Marchants described it, gave it to the illustrators, and if there was enough supplied it to Bourdelin for analysis.
Jean Marchant preserved unusual specimens in his cabinet at the Jardin royal. The final description, however, was the collective business of the Academy. While the Marchants read their preliminary drafts aloud at meetings, academicians looked at the plant and proposed improvements; during the spring of 1668 Nicolas Marchant and Duclos debated correct descriptive style. The Academy soon approved a division of labor that persisted for several decades. The Marchants grew plants, not just rare ones, in order to explain their cultivation and development. Bourdelin analyzed plants chemically, while Dodart and the Marchants compiled comprehensive nomenclatures of each plant and wrote descriptions. Finally, the artists drew and engraved the plants, working from life whenever possible. These patterns of work survived changes in the directorship, making the natural history of plants a team project that reflected the ideas and work of several academicians. It was too ambitious an undertaking for any one savant.
Illustrations occupied a prominent place in the natural history and in publicity for the Academy. Engravings of rare plants accompanied Marchant's Descriptions de quelques plantes nouvelles and Dodart's Mémoires des plantes ; they were printed in an expensive folio format that would appeal to the king and encourage him to continue publishing the Academy's work. With the same purpose in mind, academicians showed Louis drawings of plants when he visited the Library in 1681. Illustrations were essential because even the clearest description could not identify a plant so well as a picture of it. John Ray had likened "a history of plants without figures" to "a book of geography without maps," and regretted that engravings were beyond his means; Robert Morison impoverished himself to illustrate his text. Royal funding gave the Academy a distinct advantage over savants who lacked patronage, because the Academy could spend substantial sums on illustrations.
Three engravers — Abraham Bosse, Nicolas Robert, and Louis Claude de Chastillon — shared the work, which cost more than 25,000 livres (table 8)from 1668 through 1699. Like so much of the Academy's program, this too suffered from Louis's wars, and Colbert stopped paying for engravings in 1681, despite the pleas of academicians. Louvois reinstated funding for the Academy's illustrations and Pontchartrain continued it, concentrating his resources on Tournefort's Élémens and finally publishing all of the Academy's engravings of plants in the early eighteenth century. But many of the plants that Bosse, Robert, and Chastillon drew were never engraved.
Academicians tried, not altogether successfully, to hold Bosse, Robert,
and Chastillon to a new standard of scientific accuracy. They supervised the artists closely, comparing drawings and engravings with descriptions and actual plants. They were especially critical of Bosse's work, finding not one of the flowers of Cymbalaria (fig. 3) accurate, protesting the superfluous branch and pot in the picture of Gentianella (fig. 6), and deriding his anthropomorphic Mandragora mas (fig. 7) as "a ridiculous affectation." Chastillon misrepresented the proportions of the leaves to the plant in depicting the mimosa (fig. 1). Microscope and loupe were called for to correct certain features. Extraneous details such as butterflies (fig. 9) and birds marred some illustrations. Chinese characters (fig. 12) betray an engraving taken from an illustration rather than life. Many pictures lacked roots, seeds, and proper scientific names. For reasons of economy, the size of engravings was reduced under Louvois, but for reasons of accuracy, a picture of the seed, flower, and other parts of plants was added to some illustrations (figs. 1, 2). These problems slowed the work, and the engravings as published in 1701 were far from representing the standards of the Academy.
Bourdelin performed the chemical analyses, which the entire Academy reviewed and Dodart interpreted. As soon as the laboratory was minimally equipped in June 1668 Bourdelin began distilling plants, which remained his major occupation until his death in 1699. Indeed, Bourdelin analyzed more plants than were described or illustrated and his reports became a regular fixture at meetings. It took large quantities — a hundred livres according to Dodart's estimate — to analyze a plant thoroughly. Plants that did not grow around Paris. were cultivated in the Jardin royal or were purchased. From Bourdelin's findings Dodart tried to discern the basic composition of plants. Interpretation depended on minutiae, and Dodart struggled unsuccessfully to extract from overly plentiful details the generalizations that would justify Bourdelin's labors.
Academicians collaborated in planning and researching the natural history of plants, and this cooperative spirit was a matter of pride. Four members designed the research, four carried it out, and many others contributed at assemblies. Bourdelin, Nicolas and Jean Marchant, and Dodart were the principal collaborators. Although Perrault proposed the project in 1668, he worked primarily on the natural history of animals, which he had suggested at the same time. But it is odd that Duclos, who directed the project in the 1660s and early 1670s, contributed very little afterwards to its completion. The explanation does not lie wholly in Duclos's preference for other work, such as his study of mineral waters, which distracted him from the natural history of plants. Rather, his
disassociation from the natural history was involuntary, the result of a struggle over who would edit the project.
Duclos's nemesis was the young Dodart, physician and protégé of Perrault, whose association with the Academy began in 1671. Dodart quickly took a position of responsibility and leadership. He was instrumental in reinstating the practice of keeping minutes and in reviving the Academy during an early slump. Within five years he had become director of the natural history of plants, and his Mémoires des plantes reveals his control rather than Duclos's. With Perrault's protection, his influence transcended his lack of seniority in the Academy.
Dodart rose at the expense of Duclos. Director of the botanical project and leading theoretician of chemical research at the Academy in the 1660s, Duclos found his authority diminished during the 1670s. The minutes chart this decline. In his heyday from 1667 until 1669, Duclos read an average of more than three substantial papers a year — on topics ranging from coagulation and solvents to a detailed analysis of one of Boyle's books — filling roughly five hundred pages of minutes. During his decline in the period from 1675 to 1683, Duclos presented an average of fewer than two papers a year, and these fill at most twenty-odd pages in the minutes. In the 1660s Duclos dominated chemical and botanical planning with his long-range proposals, the status symbols that were the preserve of members who controlled the facilities and supervised others. Thereafter, this became Dodart's prerogative. Duclos conducted only his personal research by the mid-1670s, while Dodart supervised some of the work in chemistry and directed the natural history of plants. Why did this happen?
Dodart's interests and relative youth made him a plausible replacement for Duclos as director of the natural history of plants. Duclos's papers focused on experimental or theoretical chemistry, while Dodart was fascinated with all natural phenomena. Dodart supervised the natural history and chemical analysis of plants energetically. Duclos, however, was preoccupied with his books on mineral waters and on alchemical subjects. Since Duclos was at least thirty-five years older than Dodart, his flagging energy and waning interest in all but his favorite projects make Dodart's assumption of the natural history of plants even more understandable. Yet Duclos did not happily relinquish his responsibility to the new junior colleague. Thus Dodart's interests and qualifications do not explain a succession that was forced rather than amicable.
Duclos's espousal of Platonist and Paracelsian views and his lifelong alchemical study complete the explanation. He made no secret of these interests, which he presented to his colleagues in several papers during the 1660s. For a while the Academy tolerated Duclos's pursuits. Later it feared embarrassment should his leanings become associated in the public mind with the institution itself, and academicians went so far as to refuse Duclos permission to publish one of his books.
Duclos deeply resented Dodart's usurpation and counterattacked by maligning his editorial, scholarly, and collegial integrity. He accused Dodart of writing badly and reproached him for ignorance and careless reasoning. He unfairly denied that the Academy asked Dodart to write the Mémoires des plantes . Most important, Duclos criticized Dodart for misrepresenting the Academy. Dodart, he claimed, attributed ideas improperly to the Academy, represented his own views as those of his colleagues, portrayed the opinions of a few as if all academicians accepted them, and misrepresented theories he did not share. Duclos claimed that Dodart failed to collaborate with other academicians who had directed the research. The truth was that Dodart had simply rejected many of Duclos's views. Finally, Duclos was appalled because Dodart's book elaborated methodological issues instead of presenting conclusions about the nature of plants. At the heart of their disagreement was an argument about the purpose of analyzing plants chemically: Duclos had anticipated substantial insights into the nature of plants, but Dodart found the analyses more beneficial for medicine. Duclos's animosity, therefore, had both personal and professional aspects; the latter, which focused on the purposes of chemical analysis, will become clearer in the following chapter.
Dodart certainly used his editorial power to alter the project, and his Mémoires des plantes was a very different book from anything Perrault or Duclos had conceived. It enumerated the obstacles to carrying out Duclos's instructions of 1668. In contrast, Marchant's Descriptions de quelques plantes nouvelles simply ignored them. Duclos had hoped to establish from the chemical analyses a theory with practical applications, but Dodart declared such efforts fruitless and advocated a more pragmatic use of Bourdelin's findings. It is not surprising therefore that Duclos perceived the book as a disavowal of his views.
Dodart claimed that the Mémoires des plantes was the first stage of a more comprehensive study of plants and a showpiece of collaboration.
Both claims were only partly correct. The Academy never published the natural history of plants as conceived, and its cooperative research foundered on personal and substantial quarrels. Several problems imperiled the project. There was no perfect correspondence between descriptions and illustrations, with some plants described but not engraved and others engraved but not described. Funding was inadequate. Academicians disagreed about the style and content of descriptions, had to invent a botanical vernacular, and lacked simple criteria for selecting plants. Despite repeated revisions, illustrations remained inadequate and descriptions did not reflect the Academy's recommendations. The surviving notes reveal disagreements and delays in correcting problems.
Still another issue — the chemical analysis of plants — divided academicians and jeopardized the natural history. Academicians' expectations and difficulties form the subject of the next chapter, which explains why they persisted with such recalcitrant research.
Justifying the Chemical Analysis of Plants
The most controversial aspect of the Academy's natural history was the chemical analysis of plants. This introduced an element of causal explanation that Perrault believed was inappropriate. Even Duclos and Dodart, who approved chemical analysis, disagreed about its usefulness in the project. The results were difficult to interpret, and academicians did not know what precisely they were seeking as causes. Exacting but of uncertain merit, the chemical analyses of plants were debated by academicians throughout the remainder of the century.
The method of analysis was distillation. There was no initial dispute about this choice, for it was the traditional way to define the composition of mineral waters and to extract from animals and vegetables certain ingredients for medicaments. Chemists at the Jardin royal had given public demonstrations of distillations in their course on chemistry, and treatises by William Davison, Christophe Glaser, and Sébastien Matte La Faveur described the methods used there. Employing similar procedures, Bourdelin distilled plants for the Academy until his death. Interpreting his data and improving his method were the concern of several other academicians.
The Academy's chemical research has traditionally been dismissed as a waste of resources, thus falsely obviating the need for a closer examination of its institutional role. The number of academicians involved and the amounts of time and money devoted to the project show that the Academy regarded this work as important. Although academicians argued among themselves or admitted that they could not interpret their findings, they still
persevered with the research and refined Bourdelin's techniques of distillation. Personnel, method, and goals forced the Academy to persist with a project many members found unrewarding.
The Controversy Over Distillation
Distillation — the process whereby plants were placed in a receptacle and heated to obtain liquid and solid products — was the obvious choice for analyzing plants. It was also known to be flawed. Academicians had to justify their choice in the face of well-aired criticisms, but the shortcomings of distillation were most forcefully presented to them by their own research. Its defenders argued not only against contemporary chemical literature but also against objections raised within the Academy itself.
Duclos was the first academician to explain how to distill plants. He described in detail how to extract the chemical constituents of plants, that is, "their distilled waters, their acrid, sulphurous, acidic, and mercurial spirits, their oils, and their fixed or volatile salts." In explaining how distillation worked, Duclos used the kind of old-fashioned teleological language that Perrault and Mariotte sometimes ridiculed: the heat of the fire, he argued, made an impression on the plant and then rarefied it; rarefied matter would rise, but some matter was more disposed to rise than others. Duclos's subsequent dismissal as director of the project, however, meant that others had to defend the method he had chosen, and they did so in very different language. Dodart argued the case in his Mémoires des plantes, Mariotte used the results in his Végétation des plantes, Homberg tried to exonerate Bourdelin, Tournefort studied Bourdelin's method and findings, and Fontenelle summarized some of the arguments for distillation when he wrote the Histoire .
Two analogies seemed to warrant the distillation of plants. Distillation could be considered the equivalent of dissection (with the fire serving as the knife) or as the counterpart of digestion (with the still replacing the stomach). These were variations of ideas that had been current since Paracelsus. Nicolas Lémery, John Ray, and Nicaise Le Febvre, among others, had advocated "anatomizing" plants by distilling them; Le Febvre also emphasized that distillation would show how the heat of the stomach acted on the food it digested. But the analogy with the stomach also drew attention to some shortcomings of distillation: a fire could not transform plants the way the stomach could, did not extract the same nourishing substances, and required higher temperatures. These analogies reveal not only academicians' assumptions but also their motives. They wanted to
anatomize plants in order to understand the secrets of their structure and to know what caused their effects on humans.
Even more revealing than such justifications are the Academy's debates about the shortcomings of distillation. One difficulty was that the products were not necessarily extracted in their purest forms. Because chemists could not always tell when the distillants changed in nature from one substance to another, in any single distillation they would get mixed substances as well as relatively pure ones. Dodart expected that this problem was not serious, because even mixtures would reveal information about the composition of a plant. Obtaining pure distillants was not the original goal: the Academy wanted to discover the constitution of plants.
Another problem was that distillation was destructive. Analyzing plants destroyed the very components that produced the effects — nutritive, gustatory, poisonous, or medicinal — academicians sought to understand. Dodart responded that such effects did not necessarily result from "the union of all the principles [that is, chemical constituents]," and, anyway, that effects "which depend on several of these principles joined together often depend on the dominant principle." He did not deny that the fire itself might pass through the apparatus and mix with the plants, but he replied that even so distillants differed from one another. So long as the fire and the vessels were the same, any variations must derive from the plants and not from the distillation.
The most common objection was that, since all plants released the same constituents, these could not account for diversity among plants. Dodart, in reply, pointed out subtle differences in the proportions and strengths of the constituents. He hoped that some of the "more ordinary effects" of plants might thus be explained and that, with more experiments, unusual effects might become understandable. Mariotte, in contrast, granted the premise on which the objection rested but was more interested in why all plants had the same basic constituents. He concluded — using a thought-experiment that resembled an actual experiment described by Helmont and Boyle — that all plants had the same "gross and sensible" constituents because they received their nourishment from the same sources, earth and water.
Where academicians sought diversity — in the products of distillation — they found uniformity. Where uniformity was essential — in the replicability of experiments — they found diversity. They recognized the importance of being able to reproduce experimental results. Bourdelin weighed the plants he distilled and the products he extracted from them; he recorded the exact conditions of each distillation, including, as best he could, the temperature
of the fire. But even with all his precautions, the results of iterated experiments might vary, in some cases dramatically. Dodart tried to minimize this discrepancy by saying that chemists were entitled to ignore small variations and should take only major ones as significant.
Unexpected variations in the results of similar experiments aggravated still another problem — the unmanageability of the data. Even by 1676, when Bourdelin had been distilling plants for only eight years, academicians found the amount of information compiled from his distillations so vast as to defy their analytical skills. The responsibility of interpreting Bourdelin's data fell on Dodart, who did his best to extrapolate a few generalizations from them.
The most threatening objection, however, was that the fire created new substances instead of merely separating substances that already existed in the plant. This view was widely accepted and had been asserted by numerous English scientists throughout the century. Some academicians feared that this was indeed happening, and Dodart had to acknowledge certain disadvantages of distillation in refuting this view. As Fontenelle later pointed out, something as violent as fire must alter the constituents of a plant, especially the fixed salts, which were obtained by lessives only after calcination. Mariotte suspected that distillation might fix volatile salts and make fixed ones volatile; the fire could even create a poisonous substance from a nutritious plant or form new chemical unions from the plant's constituents. On the whole, however, Mariotte believed that fire did not produce the constituents found in plants, because all of them could also be obtained naturally without recourse to fire.
This problem worried academicians, who searched the data for reassurance. Even Duclos changed his mind about the effects of distillation. In 1668 he had believed that the fire assembled similar elements and separated dissimilar ones when heat excited motion in the substance being distilled. By 1676 he came to believe that fire changed a plant's material virtues without making its formal and specific virtues better known. Homberg later wrote that fire united some parts of a plant to form oil. Against such views, Dodart argued that a fire did not often create new products, although he admitted that it might change the structure of the basic particles that compose plants and that some elements might escape through the vessels. Dodart tried to define the nature and limits of any changes that fire could produce and asserted that any loss from the vessels was inconsequential with respect to both weight and character.
Academicians criticized the procedure they had selected, and they disagreed about continuing to use it. Whatever doubts existed when the
project started were not assuaged as it progressed; rather, Bourdelin's research brought to light still more problems. As a result, his colleagues considered abandoning or refining the method, sought a more effective one, and in the meantime changed Bourdelin's procedures.
The Method of Distillation
Bourdelin's first technique was to distill a plant and collect the distillant in a single container. He then subjected the product to further operations in order to separate it into spirit, oil, salt, phlegm, and earth. This was plant distillation as Le Febvre had taught it at the Jardin royal, and Duclos recommended the same procedures to the Academy in 1668. Duclos described how to change the temperature of the fire, explained that the ashy residue (the teste-morte or charbon ) in the receptacle containing the plant was to be calcinated and lixiviated to extract salts, and recommended that various distillants be tested with color reactors similar to those he used for mineral waters. The distinguishing feature of this method was that the distillant was collected in one container, to be separated and analyzed later. Forty-two plants were examined this way in 1670.
In 1670, shortly before Dodart joined the Academy, Duclos's method was abandoned for one that obtained more varied products. The new procedure changed the recipient (the glass receptacle that collected the distillant) every time the heat of the fire changed, Bourdelin varied this second method over the next three decades, while other academicians tried to improve it. By the time Dodart wrote the Mémoires des plantes, more than one hundred plants had been analyzed this way.
Dodart described this new technique, which he in fact revised, in some detail. He named the vessels used, told how to regulate the fire, discussed the substances obtained, and described how the ashes were treated. Everything was distilled in a glass or earthenware retort, to which was attached either a balon à tétine or a balon sans tétine, that is, a recipient with or without an udder-like protrusion. Organic matter was placed in the retort, the recipient was attached, and the retort was placed over a fire. Bourdelin regulated the fire and changed the recipient carefully.
We start the fire so slowly that it can scarcely heat the retort. We increase it slightly until some liquid passes into the receiver, and we keep the fire in this state. We increase the heat only when scarcely any more liquid comes out. We increase it slightly degree by degree during a period of fourteen or fifteen days, and we make it as hot as possible. We empty the receiver, not only whenever we
increase the fire, but more often, and we keep all parts of the distillant separated.
Distillation continued until the fire had reached its maximum temperature and no more liquid would come out. Then the ashes remaining in the retort were removed and treated. As many as fourteen different distillants might be extracted from the plant, in this order: sharp (acres ) spirits; essential oils, given by aromatic plants; sulphurous spirits; simple waters; waters with a hidden taste of acid or sulphur; acid spirits; mixed spirits; urinous spirits, either with or without acid; volatile salts; black oils; fixed or saline or lixivial salt; and earth. These products were tested with color reactors and by other means to classify them further. Each watery liquid was characterized as either "insipid, acid, sulphurous, urinous, or mixed." All the insipid liquids were combined and set aside, then all the acid liquids were combined and set aside, and so on. Once all the products had been identified and organized, each was examined for its weight and other observable properties (propriétés sensibles ).
This new method was not an invention of the Academy, but academicians applied it more rigorously than did their contemporaries. Glaser, for example, also changed recipients during distillation, but not so frequently, and as a result he did not obtain so many different distillants. But Glaser and Dodart had different purposes. Glaser simply wanted to extract certain substances that he could use as medicaments, whereas academicians wanted to identify all the constituents of plants.
By the 1690s, when Tournefort studied Bourdelin's research, the chemist had abbreviated his procedures. He removed the branches and juices from a plant and crushed it before distilling it. Then he put five livres of the plant in a tinned cucurbit, covered it with a glass head, and placed it in a water bath or a steam bath for two to three days, with the fire going day and night. Bourdelin next tested the liquid products with his repertory of indicators to determine whether they were acid or alkali. Next he distilled the dry residue in a retort with a large balloon or recipient, increasing the fire gradually. After twelve or fourteen hours he put the distillant in a glass alembic and attached a new recipient to the retort. He increased the heat of the fire and collected further distillants, separating them with a large glass funnel. By this time, the chemist was no longer regulating the fire and treating the teste-morte as he had in the 1670s, and distillations lasted only a few days instead of a fortnight. The changes perhaps reflect his declining stamina.
Bourdelin's procedures never satisfied academicians, who suggested either embellishing or replacing distillation. Dodart was frankly overwhelmed by the data and asked Bourdelin to focus his work. By distilling
more selectively, he would avert interminable research. Thus Dodart abandoned a Baconian search for every possible phenomenon. Instead he adopted a more carefully designed program that chose the objects of inquiry according to some preconceptions. Dodart's stamp was felt on the Academy's choice of plants for distillation thereafter.
Chemical analyses, like dissections of animals, required painstaking work and could be dangerous or unpleasant. Just as a slip of the knife might cause an infection (like the one that killed Perrault, who cut himself while dissecting a camel), so distillants were risky, for chemists identified many of them by taste. Rotting corpses and distilled plants stank. Anatomists treated decaying flesh with eau de vie, and Bourdelin treated plants by digesting (that is, heating without boiling), fermenting, or macerating before he distilled them. Unfortunately, this treatment altered them. Dodart wanted to assess any changes caused by prior treatment, but other academicians tried to overcome any effects. Perrault thought this could be accomplished by distilling macerated or digested plants over lower heat for a longer time. His idea was to compensate for the diminished force of the fire by increasing the duration of the distillation, a principle of substitution that he derived from mechanics.
The quest for a more satisfactory method of analysis continued well after the Mémoires des plantes appeared, but with few new ideas. By mid-November 1678, Bourdelin was on the defensive. He may well have been resisting pressure to disband his distillations. Borelly reflected on Bourdelin's recalcitrant research in the 1680s (as Homberg would do in the 1690s), probably as a result of a ministerial request. He stressed ways of rectifying distillants and designed a furnace for extracting substances from the testes-mortes . Above all he favored solvents for analysis. Some academicians had high hopes for his work. La Hire, for example, wrote to Huygens that Borelly "is searching as hard as he can for new ways of testing the liquids extracted in analyses." The chemist had discovered "something very curious," but La Hire's ignorance of chemistry prevented him from explaining Borelly's discovery.
For years after Dodart published the Mémoires des plantes, academicians debated distillation. They were so dissatisfied that they nearly abandoned it. Researchers could not be certain that their methods were adequate or that their results were meaningful. Instead of rejecting distillation, however, they refined the process.
Given the pervasive skepticism about distillation by fire, why did academicians not discard it in favor of alternative methods? They could have
tested the natural juices of plants with color reactors, observed the crystals formed by plant juices, studied vegetable dyes, or used solvent analysis. Duclos, Dodart, and Perrault had discussed the first three of these techniques, while Borelly and Duclos promoted extraction by solvents. But two academicians — Bourdelin and Dodart — saw to it that the Academy continued distilling plants, in spite of shortcomings and alternatives.
Bourdelin's influence is surprising, because his role in the institution was so circumscribed. Of all the academicians involved with the natural history of plants only the two Marchants had as little power as Bourdelin. After the 1660s, his contributions to meetings were confined almost entirely to reporting on his distillations. His early papers on chemical research were ignored by the Academy, and his notebooks record experiments made according to the instructions of Duclos, Dodart, Borelly, and others. Yet if he could not initiate research, he could veto it, and he was markedly reluctant throughout the century to use any method of analysis other than distillation. Dodart suggested that soils be lixiviated instead of distilled, but Bourdelin continued distilling them, and when Borelly criticized him for this, Bourdelin stopped analyzing soils altogether. Both Duclos and Borelly wanted to use solvents, but again Bourdelin resisted. Since no other academician was willing to devote all his time to analyzing plants, animals, and minerals chemically, Bourdelin was able by default to perfect his chosen technique.
Dodart, too, favored distillation, and as director of the natural history his opinion carried weight. Distillation seemed appropriate for two reasons: it was a universal method which permitted comparison of all plants according to a single standard, and it promised insights into how food nourished and medicines cured the body. Bourdelin's analyses hence seemed promising to Dodart's own research, and because the natural history could not proceed without Dodart and Bourdelin, their advocacy was decisive.
The most touted but controversial alternative to distillation was solvent analysis. Duclos had originally laid out a narrow sphere for solvent analysis in 1668. Distillation by fire, he argued, was best for separating the chemical constituents of most substances. The exceptions were "fixed substances and those which cannot be burned." These required "dissolving menstruums which break up the mass and render the constituent parts separable." Any substance that a fire could not distill required analysis with solvents. Pure earths, metals, glass, chalk, and minerals were all "fixed" in varying degrees; solvents offered the only hope of analyzing them.
Duclos's interest in the subject had Paracelsian origins, and he supplied the recipe for what he claimed was the true alkahest or universal solvent.
Solvent analysis was one of the issues that alienated Duclos from Dodart. The two argued about solvents in the early 1670s. When Dodart came across Duclos's recipe for the universal solvent, he mocked it as worthless for analyzing plants. In January 1675 he derisively asked the chemist to consider whether the solvent might shed light on the "marvelous effects" attributed to plants. Duclos's recipe, Dodart maintained, was as enigmatic as those of Paracelsus, Helmont, or Deiconti. Even if it was possible to make a universal solvent, it "would not help us understand the nature of plants any better, because each plant would be reduced by the operation of these solvents to a state" in which it would be indistinguishable from any other plant so treated. He derided universal solvents as being as useless as the theories of signatures and temperaments.
This exchange occurred after Duclos modified his view. He now believed that solvent analysis offered
a much better method than that of the fire since a solvent does not alter things, but leaves them as they are and reduces them to their constituent principles while preserving their virtues and their specific properties, something the fire cannot do.
Furious at Dodart's attack, Duclos criticized "the author of the project who always speaks in the name of the Company without being so charged" for having characterized "universal solvents as vain and useless." Dodart embarrassed the Academy, he claimed, by representing it as mistrustful of methods recommended by "famous chemists." Ironically, it was Duclos who discomfited his colleagues by publishing his alchemical Dissertation sur les principes des mixtes in Amsterdam after a committee of academicians had advised against its publication.
Duclos's alchemical interests made him an unconvincing proponent of solvent analysis. Borelly, however, was untainted by Paracelsianism and he too favored solvents over distillation. Like Duclos he collected reports about their use, and the year after Duclos died Borelly proposed that all kinds of solvents be prepared. Perhaps he hoped to convince his wary colleagues that solvent analysis did not necessarily depend on alchemical precepts. But his death in 1689 left the field to Bourdelin and Dodart.
Why did the Academy continue to analyze plants? Members recognized the shortcomings of distillation and its results baffled them, but they mistrusted solution analysis more. Why did they persist? The answer does
not lie merely in the persuasiveness of the method's proponents, who brushed aside problems as due to imprecise observations. Rather, the steadfast analysis of plants by academicians in the face of apparent failure results from the high premium they placed on the basic goals of chemical analysis.
The Goals of Chemical Analysis
Academicians had many reasons for analyzing plants. They hoped to find support for a particular theory of matter, to discover the nature of plants, to ascertain the medical and nutritional uses of plants and their products, to distinguish among the parts and types of plants, and to determine the limits of the method itself. Over a period of thirty-three years, more than half a dozen different goals were enunciated by the eight or nine men concerned with analyzing plants. What induced academicians to justify their research with such varied reasons? Were there differences of opinion, or did opinion change gradually during three decades? The sources indicate that some academicians did disagree about the aims of this research and that their attitudes often changed as the research unfolded, but that they never totally abandoned certain fundamental expectations.
Perrault was the first to articulate goals. Chemical analysis had two objects for him. First, he hoped to obtain some experimental support for the corpuscular theory of matter. Perrault believed that the shapes of salt crystals were related to the shapes of corpuscles, an idea shared by Lémery and Homberg. Although Mariotte later agreed that chemical analysis might prove that corpuscles existed, this view never caught on in the Academy. Perrault's second goal struck a more sympathetic chord among his colleagues: he wished to identify what caused the properties of plants, that is, what made some nutritious, others medicinal, and still others poisonous.
Perrault's ideas anticipate the three major goals that motivated academicians until the end of the century: to identify the constituents of plants, to improve medicine, and to understand how plants nourish humans. The Academy's chemical analyses of plants promised both theoretical and practical results, with the latter contingent on the former. Duclos, for example, hoped to describe the "constitution" of plants, while Dodart wanted to uncover "what plants are" and thought that chemical analysis might reveal the intimate structure in plants that produces their effects.
The main purpose of analyzing plants chemically was to discover their constituents. But by the mid-1670s, frustrated by distillation, some
academicians became disillusioned about the prospects of understanding the nature of plants. Instead they emphasized more practical purposes, such as improving medicine, without the benefit of an improved theory. Rather than try to put a practical art on a firm theoretical basis, they would operate pragmatically. Instead of deducing the effects of plants from general constituents, they would simply test specific distillants. Bourdelin's reports often prompted discussions of remedies that could be made from the plant in question. Dodart scrutinized Bourdelin's notebooks for any pharmacological benefits, and Homberg told Bignon that he expected to find some medical uses for the distillants that Bourdelin had identified. Dodart also proposed feeding poisonous plants to animals and dissecting the victims to trace the action of the poisons. He even considered carrying practical inquiry to the extreme, reversing the order of the inquiry: he suggested that pharmacological discoveries might clarify what plants were in themselves, that causes could be inferred from their effects. The difficulties of such an approach, however, were daunting.
The third major goal — understanding nutrition — was Dodart's particular interest. Indeed, the experiment for which he is probably best known stemmed from this quest: Dodart weighed himself before and after his Lenten fast, measured his daily intake of food and liquid, compared it with what he excreted, and concluded that the additional weight loss was due to transpiration. Seizing the opportunity to get comparative information when Roemer traveled to England in 1679, Dodart asked his colleague to find out how racehorses were fed and trained, to look into the training and eating habits of men and women who were long distance runners, to find out how patients were fed in hospitals, to discover whether oatmeal was mixed with cucumber or fruit, and to let him know the eating and drinking habits of the Scots and Irish. Furthermore, Dodart hoped that chemical analysis would clarify the food chain linking soil, plants, animals, and humans. Finally, Bourdelin distilled various fruits, grains, and green vegetables for Dodart in the hope of identifying what made them wholesome. But these analyses did not reflect what was already known about plants. Dodart noticed that nourishing fruits, like peaches and apples, seemed to contain only water and yielded little oil during distillation. Because these distillants could not account for the food value of the fruits, however, Dodart concluded that there must be a fixed oil in peaches and apples that only the stomach could extract.
After 1675, when it was clear that the primary goal of understanding the nature of plants would not swiftly be achieved, academicians devoted more attention to the second and third goals. They also posed more specific
questions, about the salts and oils in plants and about the chemical differences between various parts of plants. As a result, Bourdelin no longer tried to analyze every possible plant with utmost thoroughness; instead he selected particular plants or distillants for particular purposes, often those suggested by his colleagues. Dodart believed that in addressing such small questions academicians had made the best of things: while they could not, for example, explain why acidic and sulphurous substances differed, they had at least contributed to knowledge about the two. Furthermore, by concentrating on simpler problems first, academicians might establish a basis for examining the more complex issues.
In summary, the Academy's chemical analysis of plants changed in the 1670s. In the first half of the decade, as before, the principal reason for analyzing plants was to determine their chemical constituents. In the second half and thereafter, Dodart's two practical interests — nutrition and medicine — dominated chemical analysis. When academicians sought to identify the nature of plants, they were propounding an unanswerable question, given their methods and knowledge. This failure consequently forced them to pose more limited, manageable questions and to refine further their methods of analysis. These strategies, however, did not solve the quite different problem of how to present unsuccessful work to the public in a favorable light.
Publicity and Discretion
The natural history of plants was plagued by uncertainty. Academicians, therefore, continually modified their goals and research procedures. Neither perfectionists nor pedants, academicians were realistic experimentalists. The blend of tradition and innovation in their project, the too general nature of their first goal, and the unsuitability of distillation for their work, all disrupted their research. So did rivalry among colleagues.
At the very time when the Academy had decided to publish its results, its members were raising the most serious objections to the project. Dodart was dissatisfied about chemical analysis: "Since it scarcely seems that the distillants obtained by the analyses show us what plants are and what they can do, we must at least learn from the analyses what can be done, by any method whatever." This justified persistence but allowed only a small hope that more general conclusions might be reached.
Dodart was desperate because he was editing the Mémoires des plantes for publication. Some engravings and descriptions of plants were ready, but Bourdelin's research evaded all efforts at interpretation. Yet Dodart had to
present the Academy's work in the best possible light. After all, the Company was not ten years old, and savants in England and elsewhere awaited its publications eagerly but with skepticism. Everyone knew of the generous royal funding, academicians' pensions, and the institution's grandiose plans, but there had already been rumors of dissension. The public would judge the fledgling society by its publications. The Academy's natural history of plants seemed to meet a scientific need, and its chemical analyses made it somewhat innovative. But in 1675, the year when he was writing a first installment of the natural history of plants, Dodart was worried.
The Mémoires des plantes reflects Dodart's ambivalence about analysis, but it puts the best possible face on the Academy's work. Dodart addressed the problem directly. In the preface he invited the public to send information to the Academy. In the text he laid out Bourdelin's methods and results, the original goal and its more realistic modifications, and the difficulties encountered. Defending the Academy, Dodart pointed out that its laboratory had extracted several new substances from plants. Furthermore, he asserted that even if the Academy could not demonstrate "what is in each plant," then showing at least what plants are good for
constitutes an important aspect of the History of Nature, and should add considerably to materia medica, as will be seen in the rest of this work. That is the sole certain usefulness which the Company anticipated from this research, leaving the rest to the conjectures of the Natural Philosophers.
Dodart adroitly defended the Academy's failed chemical analysis. Its accomplishments, he argued, were well within the proper limits of natural history, while its failures belonged to the realm of natural philosophy and thus lay outside the scope of the project. Finally, he stressed the practical applications of the Academy's work.
The Mémoires des plantes was a clever smoke screen meant to make a good impression on the public. It emphasized the most plausible aspects of the Academy's work. But a careful reader would have realized that academicians still hoped that distillations might reveal the composition of organic matter. Indeed, Dodart's views were often confused and inconsistent because he was trying to do justice to the more ambitious goals of the Academy without making it look foolish.
The Academy had many reasons for asking Bourdelin to analyze plants. Principally, it hoped to discover the basic chemical constituents of plants, to
develop new medicaments, and to understand what makes plants nutritious or poisonous. These purposes, along with other, secondary goals, explain why academicians persisted with this research on plants. Even though they worried that what they did might be fruitless, their multiple goals made them flexible and optimistic. They could justify distillation on medical grounds, for example, and hope that it would also explain the constituents of organic matter. They continued because what they sought was so important, because alternative methods seemed even more doubtful (to all but Duclos and Borelly), and because they thought they could perfect the one method in which most of them had any confidence at all.
For academicians and contemporaries like Grew and Boyle, chemistry was pivotal because it contributed to natural history, natural philosophy, and medicine. They hoped that chemical analysis would uncover the basic constituents of living matter and perhaps corroborate the corpuscularian theory. Their hopes dashed, academicians had to adopt more limited, practical goals; at worst chemical analysis might help generate medical reforms.
Both editorial rivalry and intellectual disputes undermined the project. Academicians disagreed about its goals and conduct, and several problems stemmed from the attempts to make the natural history innovative and to give it a theoretical foundation. Yet these obstacles were not fatal to the project, which failed for still other reasons, while Bourdelin's work was endorsed in a way that no one had anticipated.
Ministerial Intervention and an Unexpected Outcome
Once the Mémoires des plantes appeared, Dodart's control over the natural history of plants grew stronger for a time. His view that the project should be published in installments was adopted, and he chose the plants to be distilled. Throughout the 1680s he directed the project, although he could never get it published. In the 1690s Homberg and Tournefort supplanted Dodart, just as he had replaced Duclos. These new members reinvigorated research and molded it to their own interests while Dodart's responsibilities as médecin ordinaire to the king eroded his participation in the Academy; indeed by 1699 he even needed a special dispensation to receive his pension because he missed so many of the Academy's meetings. When Homberg and Tournefort entered the Academy at the end of 1691, the one investigated Bourdelin's research at the behest of the ministerial protector, while the other saw how to use Bourdelin's research himself and preempted Dodart's plans. But they were not the first to thwart Dodart, whose project was imperiled by the Dutch Wars, by highwaymen, and by an illness of the king.
The Lost Second Installment
Dodart wanted to publish essays on plants annually, or at least in regular installments. He thought that the second volume of his natural history of plants should set out generalizations and exceptions and describe individual plants. Hoping that the public would share his interest in explaining
nutrition, he planned to write not about the rare plants that intrigued Nicolas Marchant but about homely vegetables that formed part of the diet, such as "coriander, lettuce, wild and domesticated chicory, watercress, etc." (figs. 10, 11). This concern with nutrition greatly expanded the work. From 1676 to April 1678, Bourdelin analyzed more than four hundred and fifty plants and animals for Dodart. In the spring of 1679, Jean Marchant sowed more than four hundred different seeds from France and abroad, "with the object of describing them for the general history of plants."
Between August 1680 and mid-June 1681, Dodart wrote the second part of the natural history of plants and prepared three other treatises for publication. But he fell victim to a dreadful scholarly accident. All of his treatises — the second part of the natural history of plants and the works on medicine, natural philosophy, and plants — were stolen from him. Du Hamel had to explain the loss to Colbert:
…all these treatises which ought to have composed a good volume were stolen from him on his way into Paris, where he was bringing them in order to complete them for the printer; and since all the efforts which he has made to recover them have been futile, he has been obliged to redo the two most important of these treatises, and to collect from his papers anything that he can find that will help him rewrite the other works.
The highwaymen were probably so disappointed with their worthless booty that they threw it away, but Dodart had to spend the rest of the year rewriting the stolen treatises. By mid-December 1681 Du Hamel could report that among the books ready for publication were Dodart's "Deuxième partie du projet de l'histoire des plantes" and "Analyses des plantes," and Marchant's "Environ 200 descriptions de plantes gravées." The first two were apparently reconstructions of the stolen books. By December 1681, therefore, despite the theft of Dodart's manuscripts, the Academy was ready to publish three volumes pertaining to the natural history.
Why were these works never published? It cannot have been disputes about distillation that delayed publication, for by separating the "Deuxième partie" and the "Analyses des plantes," Dodart had insulated the uncontroversial aspects of the Academy's work from contamination by chemical analyses of uncertain merit. Blame for the failure to publish lies partly with the academicians and partly with their patron. Many of Marchant's descriptions were inconsistent with the plates or with earlier treatises, and discrepancies had to be resolved before publication. Financial reasons also delayed publication. Funding for the Academy diminished in the late 1670s, and in the 1680s Colbert still refused to release funds for
engravings despite persistent appeals from academicians. When the king visited the Academy at the Bibliothèque du roi in December 1681, academicians presented him a list of treatises ready for publication, to no avail. But these refusals must have been couched in encouraging terms, for academicians continued their work, and morale in the early 1680s was better than it had been a decade earlier. They lived on promises and persevered.
Even the transition from Colbert's to Louvois's ministry did not at first disrupt work on the natural history of plants. During the first thirty months of Louvois's protectorship, work continued apace, especially on engravings, which Louvois had reinstigated. Louvois encouraged academicians to ready their work for print. His ministry marked closer ties between the Academy and the Jardin royal, especially with Fagon and Tournefort, whom Fagon took under his wing. Fagon chose plants for Chastillon to draw for the Academy's "Mémoire des plantes," and Louvois sponsored Tournefort's herborizations in the Iberian peninsula. In the winter of 1684 the Company planned to work on roots, seeds, and woody parts of the plants that had been engraved, while Bourdelin continued his analyses. In 1685 and 1686 Dodart and Marchant concentrated on engravings and descriptions. In 1685 Du Hamel believed that the Academy would soon publish a volume of the natural history of plants, for which many engravings were completed. But after 1686, the grand botanical compendium was mentioned in the minutes only as a project of the past.
What explains this abrupt abandonment of the natural history of plants? Academicians had overcome editorial rivalry, discouragement about chemical analyses of uncertain merit, theft of manuscripts, and parsimony prompted by the Dutch Wars. Despite all of these discouragements, they researched and wrote for publication. But in the mid-1680s a new and more dangerous impediment arose. What jealousy, controversy, theft, or economy had not accomplished, ministerial interference did. The Academy's botanical work was injured by misguided enthusiasm on the part of its patron.
When a patron's own interests interfere with the conception or execution of a creative project, the quality of work suffers. Interference from a patron who does not understand the technical language and skills or the theoretical assumptions of the work can be especially damaging. This is precisely what happened. In 1686 Louvois intervened, upsetting the delicate
balance between theoretical and practical expectations. Academicians had hoped that their natural history of plants would benefit medicine and add to basic knowledge about the nature of the world. They disputed among themselves as to whether sound theory was a basis for or an outcome of practical advance. But no academician advocated choosing between utilitarian and abstract goals; rather they debated the precise relationship between practical and theoretical knowledge. Into this scholarly discussion was injected a ministerial command to obtain practical benefits at the expense of theoretical research.
Louvois took an interest in natural history and preferred it to the other sciences partly because he thought it promised the quickest utilitarian results. He became especially impatient when the king's life was endangered by a serious illness that his physicians had been unable to treat effectively. Looking for a scapegoat, resenting an Academy that could not save its monarch's life, needing more funds for Louis's wars, and expecting scientific inquiry to lead inexorably and swiftly to improvements in the quality of life, Louvois lost patience. He told the Academy how to do its work.
At the meeting of 30 January 1686, Henri Bessé de La Chapelle, Louvois's spokesman in the Academy, read a short paper to academicians. Willfully insulting and openly disdainful of the Academy's chemical research, La Chapelle warned academicians that they must move in new directions. He exhorted academicians to eschew "curious" research, which he called "a game" or "an amusement of the Chemists," and to apply themselves instead to "useful research that has some connection with the Service of the King and of the State. La Chapelle recommended that academicians study medicine, improve and republish Duclos's book on mineral waters, try to desalinate sea water, and analyze wines. He also discussed the relationship among medicine, natural philosophy, and the natural history of plants:
The other research more appropriate for this Company and which would be more to the taste of Monseigneur de Louvois is anything that can illustrate natural philosophy and serve medicine, these two things being practically inseparable, since medicine takes consequences and profit from the new discoveries of natural philosophy.
La Chapelle believed that the Academy's chemical analyses were worthless because they belonged not to the practical realm of botany and medicine but to the abstract and theoretical realm of natural philosophy. The Academy's natural philosophers controlled chemistry and the natural history of
plants, and they stood accused of subverting these subjects by seeking the underlying causes of things.
While La Chapelle agreed that practical results followed from theoretical discoveries, he noted that chemical research at the Academy seemed to make little progress in either direction. For that reason he warned the Academy to concentrate on empirical matters. In singling out Duclos's book on French mineral waters for praise, La Chapelle cited a work that perfectly blended science, medicine, and chauvinism to please a royal patron interested in practical accomplishments. Furthermore, Louvois and La Chapelle unerringly criticized the most vulnerable of the Academy's projects, the one that had stirred personal and theoretical controversy and whose publications were few by comparison with its cost. Whatever Louvois's motivation — Louis's nearly fatal illness, some behind-the-scenes influence, or impatience with a project much discussed but showing few practical results — his instructions were clear. Academicians were to spend more time on medical research. He would continue to support the natural history of plants only so long as the Academy adjusted its contents to his expectations.
Since Louvois never repudiated his spokesman or his instructions, he must have been content with La Chapelle's speech. Other academicians perhaps agreed, for only eighteen months later La Hire explained La Chapelle's role to Huygens, to whom he sometimes complained about Louvois's policies. Louvois, he said, had "entirely committed the care of our academy" to La Chapelle, who "does us the courtesy of attending our meetings and of communicating to us his good ideas (belles lumières ) in the sciences." La Chapelle's place in the Academy was assured and his harangue of January 1686 was heeded by academicians, up to a point.
La Chapelle's speech is a curious blend of criticism and advice, of general statements about method and specific suggestions for research, of familiarity with and ignorance about the Academy's chemical research. Many of his suggestions were superfluous. Duclos, Dodart, and Bourdelin had already studied the tastes of plant distillants, analyzed earths, and tried to desalinate sea water. Academicians had always sought medical applications of their work and planned to include the medical uses of plants in the natural history. La Chapelle named specific vegetable and mineral substances — mercury, antimony, quinine, laudanum, poppy, tea, coffee, and cocoa — for study, but academicians had already examined them. Perhaps, in his awkward double role as ministerial spokesman and as colleague of the academicians, La Chapelle was trying to soften Louvois's criticisms implicitly by proposing work he knew his colleagues had already
performed. Louvois's motives are clearer than La Chapelle's, but the effect of the speech, no matter what its genesis, was unmistakable.
La Chapelle's talk had marked repercussions. First, academicians no longer presented papers about the natural history of plants. Second, the chemists were more carefully supervised and had to draft new research proposals. Both Borelly and Dodart immediately suggested projects incorporating Louvois's requirements, and Du Hamel turned over the chemical proposals to La Chapelle in April 1686. During January 1688 Borelly was asked to keep a notebook of his chemical experiments, and he presented his findings to the Wednesday assemblies. Third, chemical analyses emphasized the potentially useful natural products of plants, such as gums and materia medica. Fourth, medical remedies became an even more common topic of discussion at meetings. Fifth, fewer plants were described or engravings verified than in previous years. Sixth, only two other papers on plants were read; one was a letter sent to academicians about a deformed pear, and the other was Sédileau's report on the insects that caused galls in the bark of trees in the royal orangerie. Thus the only botanical paper produced by an academician from 1686 until 1690 concerned a disease of Louis's orange trees, not disinterested inquiry but institutional flattery of the patron. The years 1688 and 1689 represent the nadir of botanical research in the seventeenth-century Academy. Only Bourdelin continued his normal research, perhaps because while working at home he could isolate himself from ministerial pressures. When La Hire reported the Academy's activities to Huygens in 1690, he did not mention any work on plants. By the time Pontchartrain took over the Academy from Louvois, botanical research at the Academy had very nearly collapsed.
With the decline in pure botanical research, academicians emphasized the nutritional, medical, and industrial uses of plants and their products. In 1688, 1689, and 1690, they assessed a coffee-flavored beverage brewed from roasted rye, tasted the milky juice in common chicory, considered a remedy for hemorrhoids, and compared methods of treating wood to obtain good charcoal. Only in 1690, when Louvois's health and interest in the Academy were declining, did La Hire revive the study of plant vegetation and Dodart and Marchant again read descriptions of plants. Their example was lauded by Gallois and, oddly, by La Chapelle, both of whom urged a study of roots. Despite this flurry of activity, Louvois's reprimands about curious research and chemical games had both an immediate and a lasting detrimental effect on the natural history of plants; the project temporarily came to a halt and never recovered its full vigor.
The natural history suffered from fiscal exigency and internal difficulties
both intellectual and personal, but ministerial manipulation was decisive. Indeed, theoretical botany revived when Pontchartrain became protector. In 1692 Dodart planned botanical research and read a paper on the structure of the bud of a tree, while La Hire demonstrated that fig trees produced flowers, and Tournefort and Marchant described plants for the Academy's new monthly publication. Observations sent from the Far East fired enthusiasm and broadened the scope of inquiry, so that the Academy inspected drawings of hitherto unknown Chinese plants (fig. 12) and studied the root of ginseng. Dodart reported the growth of leaves and shoots on an elm felled fifteen months earlier. Tournefort examined an unusual mushroom, the flowers of Apocynum maius syriacum rectum cornuti, and the contraction of fibers in certain plants. Morin de Toulon discussed a plant called tartunaire in Provençal, and La Hire fils described how a vine attaches itself to walls. La Hire and Sédileau studied orange trees, and Jean Marchant reported on his and his father's emendations of Bauhin's Pinax . In 1697 Dodart pointed out that the base of a tree's crown was always parallel to the ground in which the tree grew. No longer did botanical presentations emphasize utility.
Finally, Tournefort and Homberg agreed that the natural history of plants should be published, and they cooperated for a time with Dodart, Marchant, and Bourdelin. By 1692 Dodart and Marchant were once again reading descriptions of plants to assemblies almost as frequently as they had before 1686. They also compared plants with engravings, while Bourdelin analyzed plants and Homberg and Tournefort studied his findings. Homberg was initially enthusiastic and his manuscripts confirm that the Academy expected to publish the natural history of plants during the 1690s.
In the number and variety of botanical activities and in the balance of pure and applied research, the 1690s were a period of marked improvement. Ministerial appointments spurred this revival. Unlike Louvois, who named relatively unknown scientists to poorly paid positions and added no chemists or botanists to the Academy, Pontchartrain selected well-known and respected scientists — Boulduc, Homberg, Charas, and Tournefort — and paid some of them decently. At least as important, he and Bignon allowed academicians to control their research, insofar as the royal treasury could underwrite it. Finally, in appointing Tournefort, Pontchartrain injected into the Academy a savant with a forceful intellect and powerful backing who would usurp the natural history of plants and shape it to his own purposes.
A New Editor
Pontchartrain's choice of Tournefort had obvious merits. Tournefort shared many interests with Jean Marchant, Dodart, and Bourdelin, and he collaborated with other colleagues on varied research. He agreed that it was important to correct errors in traditional botanical literature and to develop the medical uses of plants. Like the Marchants, Tournefort advocated collecting information from all countries on the medicinal uses of plants; he believed that the task merited royal patronage and promised new cures for dangerous diseases. His descriptions of plants reinforced the efforts of Dodart and Jean Marchant. He studied Bourdelin's chemical analyses of plants and examined the chemical constituents of soils. He also conjectured about the constituents of mixed bodies and the medicinal properties of plants. These ideas had been the hope and despair of Duclos, Dodart, and Mariotte before him. Along with his colleagues, Tournefort tempered expectation with doubt, for he was skeptical of ascertaining the "the primary qualities" or the "configuration of the parts" of plants and soils.
Even Tournefort's Élémens de botanique complemented the Academy's other botanical research. It was an intellectual prolegomenon to the Academy's natural history, although its cost delayed publication of the latter. Tournefort classified plants and rationalized their nomenclature, did not include in his engravings "pictures of the entire plant," and omitted the "virtues" of plants from his descriptions. Thus the Élémens laid the groundwork for the Academy's natural history of plants, which Pontchartrain's and Bignon's policies seemed to revive.
Tournefort promised in the introduction to his Élémens that the compendium would soon appear:
The Royal Academy of Sciences, which has made Botany one of its principal activities, will soon furnish to the public some papers about the natural history of plants, with illustrations, descriptions, and analyses, all worthy, if one may dare to say it, of the magnificence of the King, and which will demonstrate just how far the science has been perfected.
Yet the work he predicted so confidently in 1694 was not to appear. Within four years Tournefort himself sabotaged it. His next major book, the Histoire des plantes qui naissent aux environs de Paris of 1698, superseded the Academy's natural history of plants. Thus the unexpected outcome of three decades of research was the usurpation by a new member of prerogatives clearly staked out by his colleagues.
After 1694 the Academy decided not to publish its grand natural history
of plants. Homberg retracted some of his optimistic assessments of Bourdelin's analyses, and Tournefort's Histoire des plantes announced that the Academy's natural history would never appear in the form originally conceived. Granting the importance of correcting previous botanists, Tournefort nevertheless deprecated any plan to begin "a general history of Plants on the basis of new expenses." This caution was sensible during the 1690s, but coming from the author of the costly Élémens, it must have struck some of his colleagues as unseemly and self-serving.
Tournefort's Histoire des plantes supplanted and transformed the Academy's natural history. Unlike his Élémens, which solved a problem that academicians had disregarded, the Histoire des plantes drew on the botanical work of Dodart, Bourdelin, and the Marchants. Tournefort's book grew out of his lectures at the Jardin royal and also out of the Academy's work. It credited the Marchants with supplying plants for analysis, used Bourdelin's research to delineate the medical uses of plants, and included alternative plant names such as the Marchants and Dodart had painstakingly collected. Tournefort, however, did not make their intentions his own. Instead he focused on plants in the Paris region that were medically useful. In so doing, he made an unwieldy mass of data manageable, and he captured the sentiment of academicians that the medical implications of Bourdelin's work were its most viable dimension. He also revived Duclos's idea that the Academy emphasize French flora. Eighteenth-century academicians viewed his book as the sequel to Dodart's Mémoires des plantes , while Tournefort declared it to be the first of several regional natural histories of French flora.
In effect Tournefort divided the Academy's project. In appropriating the description and analysis of useful local flora to himself, he left foreign flora to Marchant. Marchant worked until the end of his life on the old project, but after publishing 319 engravings in 1701 he got no further with its publications. When Reneaume and Terrasson tried to revive the natural history of plants in 1709, their conception of the work was considerably different from his.
Tournefort redefined the Academy's natural history of plants and welded a new alliance between the Academy of Sciences and the Royal Garden, with the latter dominating. His role in the Academy during the 1690s resembled Dodart's during the 167Os: both entered the Academy with influential mentors, assumed direction of a project that seemed to be floundering, and published specific parts of the Academy's research. Their books appeared under their own names and reflected the research of other academicians, although Dodart overstated and Tournefort minimized the
contributions of his colleagues. Tournefort isolated Marchant's work but published some of the Academy's results in forms that its original proponents could not have foreseen. When at last the engravings appeared as Les plantes du roi in the eighteenth century, they brought to an elegant close the series of publications that represented the seventeenth-century Academy's failed natural history of plants.
The Academy's corporate character affected its scientific inquiry, by providing continuity of goals across the lifetimes of individual members and by encouraging division of labor within research teams. These advantages favored ambitious projects. But the natural history of plants never came to fruition as planned because it was plagued by serious problems. The goals of research were unrealistic given the methods available. Chemical analysis was difficult to interpret. Relations among academicians were not harmonious. Funding was erratic, and manuscripts were stolen. Ministerial intervention on the side of practical rather than theoretical research damaged morale.
Neither the structural benefits of collaboration nor the relative independence of strong-minded individuals entirely surmounted these problems. Dodart and Tournefort faced a difficult choice. If they were true to the original intentions of the project, these would become a straitjacket. But if they changed its goals, reported research selectively, and published their own views rather than those of their co-workers, they alienated fellow academicians. Both chose the latter course.
By contrast the Academy's work in the natural philosophy of plants required little team effort yet achieved a modest success. It was carried out by academicians who worked independently of one another and did not always submit research plans to the institution or its protectors but instead read finished papers to their colleagues preparatory to publishing them. It enjoyed minimal material support from the institution but at least was free from ministerial interventions. In the natural history, academicians emphasized experiment and observation over theory, but the uncertain theoretical implications of that work undermined the project. In the natural philosophy, theory and experiment were more effectively wedded. If the natural history of plants tested the Academy as a company that produced science, the natural philosophy of plants revealed it as a company that reviewed what its individual members had produced. For the natural history the institution provided labor, materials, experiment, observation,
and analysis; for the natural philosophy the institution served primarily as a referee of ideas. Academicians' failures in the natural history revealed tensions between the Academy and its patrons in the seventeenth century; academicians' achievements in the natural philosophy helped establish the pattern of the Academy's activities in the eighteenth century.
In the late seventeenth century botanical thinking derived its inspiration from four sources: natural phenomena; the more or less traditional ideas that defined and constituted the field itself; ideas borrowed from other disciplines; and newly invented scientific apparatus.
The stimulus provided by natural phenomena was particularly dramatic in the early modern period because, with the discovery of the new world and the more assiduous exploration of the old, the number of plant species known to Europeans quadrupled. As a result, fifteenth-, sixteenth-, and seventeenth-century botanical literature reflects a delight in the superabundance of nature. Many botanists focused on the natural resources of the discipline, trying to record and describe all known types. Academicians contributed to this enterprise by preparing their natural history of plants.
Traditional botany provided part of the conceptual framework for students of plants, who distinguished flora from other living things in an Aristotelian manner and modeled their treatises in style and content after those of distinguished predecessors. But by the middle of the seventeenth century there was a marked shift in botanical writing away from herbals and toward specialized treatises on classification, regional flora, plant anatomy and physiology, and exotic specimens. When academicians looked backwards, it was often to disprove survivals from earlier literature that they regarded as superstitions. Insofar as they were influenced by botanical literature it was by natural histories of the recent past rather than by physiological treatises by contemporaries such as Grew or Malpighi.
In the late seventeenth century savants challenged and expanded the traditional ideas. They did so through cross-disciplinary borrowings of ideas and instruments, which provided new interpretations and phenomena for contemplation. Theories adapted from other disciplines, especially from animal anatomy and physiology, stimulated botanists to reinterpret the structure and behavior of plants. Instruments such as the microscope and air pump helped them see plants in more detail and from new perspectives. As a result of such inspirations, academicians and their contemporaries were swept up in a compelling new explanatory momentum.
Both descriptive and explanatory botanical writing drew from all four sources — the plant, the field of botany, borrowed ideas, and new apparatus — to some extent. As a result, by the eighteenth century the concepts of the plant and of botany were transformed. Natural history focused primarily on naming, describing, and classifying plants, while natural philosophy studied the processes related to the plant's life cycle, drawing heavily on theories and equipment developed in other contexts.
At the Academy the natural history was inspired primarily by natural phenomena and by ideas from traditional botany. When academicians drew on ideas from other sources, they relied on chemistry. Oddly, the natural history of plants excluded anatomy, even though this was the mainstay of the Academy's natural history of animals. Instead academicians applied any anatomical study of vegetables to their physiological theorizing. Their natural philosophy, in contrast to their natural history, depended for its inspiration principally on other disciplines, especially zoology, and on new instruments. In the end it altered the very idea of the plant itself.
Academicians focused their natural philosophical research into plants on three questions: does sap circulate in plants the way blood circulates in animals; which accounts better for plant physiology, chemical or mechanical explanation; and do the air pump and microscope clarify how plants reproduce and grow? The present chapter describes analogical reasoning and the Harveian model that caused academicians to ask the first question; the following chapters address their answers to all three questions.
The Nature and functions of Analogical Reasoning
Analogical reasoning has played an important role in the development of the sciences. As a means of explaining the unfamiliar in terms of the
familiar or of subsuming one field under the laws governing another, it has didactic and heuristic value; fertile analogical theories may enrich both the borrowing and the lending disciplines. The stimuli to reasoning from analogy may be both general and specific. In the seventeenth century, Galileo, Descartes, Newton, and others had predisposed savants to "a unitary conception of natural forces," and discoveries in many individual scientific disciplines were so impressive as to become paradigmatic for other fields as well. Thus botanists were beguiled in particular by advances in animal physiology to essay zoological methods and theories in their own domain.
Two characteristics distinguish late seventeenth-century analogical reasoning about plants and animals from earlier comparative theories. First, unlike the traditional theories of sympathies and antipathies, the new analogies provoked further tests; insofar as the model itself was experimental, so was the analogical hypothesis. Second, savants spurned the technological models and mathematical standards that many had previously favored and chose instead models and standards from the life sciences themselves. That was possible principally because the Harveian theory explaining the motions of the heart and blood offered a seductive model. Consequently, much analogical reasoning in botany reveals a double trend: toward increased experimentalism in botany and zoology and toward greater self-reliance within the biological sciences.
The most ambitious and elusive of botanical analogical leaps in the seventeenth century was the hypothesis that sap circulates in plants as blood does in animals. First propounded in 1660 by Johann Daniel Major, only one generation after William Harvey published his De motu cordis, the idea caught on quickly in England, France, and Italy. Although Nehemiah Grew and Marcello Malpighi are probably the best known adherents of the theory, they were not alone in exploring it systematically. Members of the Academy were the first to push the analogy to its limits. Claude Perrault and Edme Mariotte defended the idea at meetings of the Academy during the summer of 1668, with Nicolas Marchant demonstrating Mariotte's experiments and Samuel Cottereau Duclos opposing the hypothesis. In 1679 and 1680, Mariotte, Perrault, and Duclos published revised statements on the subject, and later in the 1680s other academicians, especially La Hire, tried to repair the analogy. Their efforts shed light on how the Academy fostered the biological sciences, on the dramatic changes in botanical research in the late seventeenth century, and on the merits of analogical reasoning.
Before examining the theory of the circulation of the sap as developed in
the Academy, a double foundation must be laid by establishing the nature of analogical reasoning and by describing the features of the Harveian model that inspired academicians. Only then can academicians' elaboration of the hypothesis be assessed.
Analogy is a means of comparing two things. By identifying similar traits in both objects, scientists infer the existence of a causal mechanism affecting both. Several types of analogy used by scientific savants have been identified by historian-philosophers of science. Claire Salomon-Bayet distinguishes "lazy-universal" from "experimental or observational" analogies; Georges Canguilhem differentiates mathematical analogies from explanation by reduction; and Mary Hesse compares formal and material analogies.
Salomon-Bayet's distinction is addressed specifically to the early modern period. Taking Paracelsianism as the exemplar, she defines lazy analogy as a mental habit of ancient origin that simply assumes untested the sympathy or antipathy of all parts of the universe. By contrast, experimental or observational analogy is open to verification and correction. Experimental analogy subsumes particular objects or phenomena under general theories either by applying the laws or theories of one discipline to another or by employing a model; the first method is more fertile than the latter, which has didactic but not explanatory power.
Canguilhem focuses on analogical reasoning in biology, contrasting deduction (or the use of mathematical models) and explanation by reduction (or the use of mechanical analogies or analogical models). The former is less naive but also less useful than the latter for biology, which is not always susceptible to expression in mathematical language. Canguilhem's discussion also clarifies Salomon-Bayet's distinction between analogy from theories and analogy from models. Two examples suggest the two kinds — structural and functional — of analogy: the stirrup and anvil after which the bones in the ear are named, and the ancient irrigation system which inspired the Greek concept of the motion of blood. Unlike Salomon-Bayet, who insists that a fertile analogy must prompt experiment or observation, Canguilhem allows that in biology analogy from models can be an alternative to experiment, because models permit "the comparison of entities which resist analysis. Both Canguilhem and Salomon-Bayet agree that models may aid the quest for laws.
Mary Hesse is interested in both the physical and the biological sciences and, unlike Canguilhem and Salomon-Bayet, systematically analyzes analogical reasoning as a logical tool appropriate in all sciences. Hesse distinguishes between material analogy and formal analogy. Material analogy
is both substantive and predictive, whereas formal analogy is neither, since it is simply a one-to-one correspondence between different interpretations of the same formal theory. Thus Hesse's analysis of material analogy is relevant to seventeenth-century botany.
Material analogy is a means of comparing different organisms or phenomena by pairing and comparing their individual traits. The model is the organism or phenomenon that is already understood; the explicandum is the organism or phenomenon that needs to be explained. A systematic comparison of their traits will determine whether the explicandum can be understood in terms of the model. Thus, if the traits in the model resemble those in the explicandum, and if the traits in the model constitute a causal mechanism, then the same causal mechanism may be inferred in the explicandum.
Hesse provides a schema for such comparisons, listing the paired traits in two columns, one for the model and one for the explicandum. Paired traits are subject to "horizontal" comparison, while the theory linking a set of traits as the causal mechanism in the model provides a "vertical" connection. The closer and more numerous the horizontal similarities between pairs, the more likely that the vertical causal chain of the model may be inferred to exist in the explicandum.
Material analogies may have explanatory power if three conditions are met. First, the model and explicandum must have something in common beyond the analogy in question, that is, there must be "pretheoretic" similarities between them. Second, their horizontal similarities must be substantial. Third, there must be a causal connection among the traits in the model.
Hesse's analysis clarifies Canguilhem's and Salomon-Bayet's distinctions. Thus the most fruitful dichotomy is not between models and the application of one discipline to another, as Salomon-Bayet argues, nor between mathematical models and explanation by reduction, as Canguilhem would have it. Rather, there are empty and productive analogies, and the latter may be either mathematical or material; but only material analogies with pretheoretic similarities may have predictive power.
Analogical reasoning has various advantages and shortcomings. As a form of induction, it is prey to all the shortcomings of the inductive method. But analogical argument enjoys a special role when observation or experiment are inadequate. In such a case, however, it is inconclusive not only for all the usual inductive reasons but also because it rests on an incomplete identification of similarities. Nevertheless, analogy offers a means of selecting
a hypothesis, because it draws attention to comparable properties that may betray causal similarities.
As differentiated from experiment, analogy permits comparisons between traits or phenomena that cannot be analyzed. Just as an experimenter uses theory to suggest predictions that do not proceed from tests and observations, so the savant uses analogy to suggest hitherto unsuspected causes or theoretical entities.
Analogy resembles theory, because it offers a way of subsuming a pattern of behavior under a set of laws, and because it holds out the promise of generating explanations and predictions. Canguilhem explains how analogies differ from experiment and are like theories:
What validates a theory is the possibility of extrapolation and prediction which it permits in directions which the experiment, keeping to its own level, would not have indicated. Similarly, models are judged and tested one against another by the completeness of the accounts they give of the properties to which they direct attention, in the object of study, and also by their aptitude for revealing properties hitherto unnoticed. The model, one could say, predicts.
In explaining this similarity of analogical reasoning to theory, Max Black's study of metaphor is useful. A metaphor is a comparison whose thrust is indefinite. So long as the scientist does not know "how far the comparison extends" and tries to push the analogy to its extreme, unexpected theoretical implications may emerge, for "it is precisely in its extension that the fruitfulness of the model may lie."
Good analogies, therefore, supplement and encourage experiments and, like theories, suggest what, unobserved, might have remained unsuspected. It sometimes happens that an analogy, like a metaphor, changes the way both the model and the thing being explained are viewed. This may be due to the impoverishment of the model, or to changes in the meanings of the concepts associated with the model and explicandum; sometimes "the two systems are seen as more like each other."
Analogical thought has influenced biological thought in both positive and negative ways, depending on how the model is selected. For example, when models are more appropriate than experiments, analogy can stimulate alternative observations or anticipate evidence that is inaccessible given experimental capabilities. But overreliance on mechanical and technological models has injured biological analysis, by emphasizing structure at the expense of function. Thus, Greek and Latin anatomical nomenclature suggests the appearance but not the function or causal mechanism of the anatomical part. Such analogies cannot "show the identity of the
general laws of the two fields of phenomena which are brought together" and thus are causally insignificant.
The risks and rewards entailed in the choice of model are illustrated in two theories of the motion of the blood. Both Harvey and the ancients explained the motion of the blood analogically. The ancients compared it to the unidirectional supply of water to irrigation channels and hence argued that blood was absorbed by the body and had to be continually replenished; their theory was conceptual, not experimental. Harvey replaced the notion of irrigation with the idea of circulation within a closed circuit, an idea that was compatible with his experimental findings. Models chosen from technology on the basis of structural resemblance are likely to lead to an explanatory cul-de-sac when applied to the biological sciences. But in the seventeenth and eighteenth centuries savants began to use biological models more often, with positive results for the life sciences and especially for plant and animal physiology.
Analogical reasoning can serve as the prelude to comparative method. This is particularly important in analogies between plants and animals, which often resemble one another functionally, but have different structures. Either similarities or differences may be emphasized, but pretheoretic resemblances determine whether the comparisons are valuable. The important point for comparative method is to test, not assume, any similarities. As will be seen in the following chapter, some academicians used analogy in precisely this fashion; starting with a comparison between plants and animals, they tested the analogy experimentally, admitting structural dissimilarities between plants and animals and investigating how plants accomplished equivalent functions in the absence of equivalent organs. In such cases, analogy identifies crucial dissimilarities and becomes a preliminary step to understanding causal differences.
Analogies are full of pitfalls for the unwary. Even scientists who rigorously examine the traits of two organisms for dissimilarities need to guard against claiming too much for an analogy. In the eighteenth century, Albrecht von Haller complained that analogy had become a substitute for experiment. This was the flaw that had weakened medicine, he believed, because "the great source of error in physics" was due to "physicians, at least a great part of them, making few or no experiments, and substituting analogy instead of them." Analogies should inspire experiment, and although they may extend it, they should not be a substitute for it. The overenthusiastic savant runs the risk of conferring "a representational value on a model" and of letting the model become axiomatic instead of being
only the lender of a mechanism. Analogies are frail inductive tools. When the identification of similarities or dissimilarities is incomplete, then the analogy is inconclusive.
In summary, analogies have more than a didactic value to scientists. They offer a means of selecting hypotheses. As a weak form of induction, they can be useful when only a few instances are known or when only sparse observational data exist. They should inspire, may supplement, and will sometimes replace experiments. They resemble theories in suggesting new experiments, subsuming the behavior of an object under a general rule, predicting, and explaining. They are fertile because, like metaphors, their extension is indefinite; when scientists push analogies to their extremes, they may discover what would otherwise have eluded them. The best analogies pay compound interest on what they have borrowed, by changing the way both the borrowing and the lending disciplines are perceived. Finally, failed analogies have a particular use: by drawing attention to crucial dissimilarities in the things being compared, they stimulate a search for the causal mechanism. Failed analogies, therefore, are the beginning of comparative method and show where further research will be necessary.
Improved analogical reasoning helped advance the biological sciences. The choice of model was important. What was needed was a broadly conceived, well developed theory, one with adequate observational and experimental supports to win adherents, and sufficient specificity to avoid sectarian splits. Chemistry was appealing, and was regarded by Paracelsus, Helmont, Boyle, and others as a source of knowledge about the basic and unchanging components of the universe, but it was beset by doctrinal divisions.
In the absence of an approved general explanatory theory, savants had recourse to smaller-scale theories with a more limited explanatory range. William Harvey's writings on the movements of the heart and blood offered just such a theory, and as his hypothesis became acceptable scientists in other fields borrowed it. In the Academy and elsewhere, botanists formulated the hypothesis that sap circulates in plants. Their analogical leap is an important case study for several reasons. It is an example of borrowing from within the biological sciences and illumines the relative importance of structural and functional analogies in botany. It indicates whether savants tested analogy experimentally and how they responded to its limitations. Finally, it reveals that when the model failed, academicians used analogy as a stimulus to comparative method and thus came to ask an important botanical question.
The Circulation of the Blood
Three theories of circulation competed in France after 1628: the hypotheses of William Harvey, Jean Riolan, and René Descartes. Harvey claimed that blood made a complete circuit of the body, that the heart pumped it into the arteries, that blood then passed to the veins and returned to the heart, and that blood nourished and heated the body. He believed that the heart, veins, and arteries were "constructed for that purpose with extreme foresight and wonderful skill," and thus that their structures revealed their functions. Descartes and Riolan accepted the idea of circulation. But they disagreed with Harvey about important details, challenging, for example, his estimate of the speed with which blood circulated. As a result, they proposed alternative explanations of the motions of the heart, and they retained certain elements from ancient theories about the motion of the blood. French botanists who wished to formulate an analogical theory of the circulation of sap had, therefore, three models from which to choose. None, however, was perfectly compatible with vegetable anatomy and physiology. These models must be clear if the theories of the circulation of the sap are to be understood.
Harvey's theory was the most important and was widely accepted in scholarly circles by the late 1660s. It was novel in several respects: it unified the venous and arterial systems, described the pulse as a mechanical effect of the heartbeat, calculated the quantity of the blood, and characterized the circulation as a closed system in which all blood returned to the heart without being consumed. Harvey challenged standard notions about the hierarchy of bodily organs. He maintained that the blood was more important than the heart because it preceded the heart in the development of a fetus. He also claimed that the heart was formed prior to the brain and liver and was thus more important to life than either of those organs.
Harvey also retained certain traditional views. He believed, for example, that the purpose of circulation was to nourish and warm the body by generating heat and spirits necessary for life. This made a circulatory motion necessary, in his view, not only so that all the parts of the body "may be nourished, warmed, and activated by the hotter, perfect, vaporous, spirituous and, so to speak, nutritious blood," but also in order to repair the blood which "may be cooled, coagulated, and be figuratively worn out" in its travels. The heart held a special, beneficial position in the body, for it was the "source or the centre of the body's economy" and could restore blood "to its erstwhile state of perfection. Therein, by the natural, powerful, fiery heat, a sort of store of life, it is re-liquefied and becomes impregnated
To prove his theory, Harvey tested and confirmed three assumptions. First, "the blood is continuously and uninterruptedly transmitted by the beat of the heart … into the arteries" in large quantities that cannot be made up by intake of food. Second, the pulse of the arteries drives the blood into every part of the body, in greater quantities than necessary for nutrition, and in such amounts that a rapid circular motion must be assumed. Finally, "the veins themselves are constantly returning this blood from each and every member to the region of the heart." As proof, Harvey cited his measurement of the amount of blood passing through the body in a half-hour; his experiments with ligatures of blood vessels; and his description of the structure and function of valves in the veins. Once the three suppositions were confirmed, Harvey could state "that the blood goes round and is returned, is driven forward and flows back, from the heart to the extremities, and thence back again to the heart, and so executes a sort of circular movement."
Although Peiresc and others in France defended Harvey's theory from the beginning, Riolan and Descartes both proposed alternative theories of the circulation of the blood. Riolan, a respected anatomist and member of the medical faculty of Paris, did not object to the idea of circulation in itself. But he found Harvey's formulation distasteful because it challenged Galen and undermined some of the theoretical bases of traditional medical practice. Riolan also mistrusted Harvey's assumption that the anatomy of animals may resemble that of humans.
Riolan argued that the blood traveled through the arteries and veins to the extremities of the body and returned to the heart two or three times a day. Not all blood returned to the heart, however, because some of it was assimilated into the body. Although the normal route of the blood was away from the heart in the arteries and to the heart in the veins, when the veins of the arms and legs threatened to become empty the blood in the veins of the trunk could flow backwards to prevent a void. Thus Riolan maintained conventionally that blood ebbed and flowed in the veins and that it was consumed as nutriment by the parts of the body.
Riolan also calculated the amount of blood in the heart and the entire body and the quantity of blood that passed through the body in one hour. But he disagreed with Harvey. Riolan did not believe that the heart propelled the blood, as Harvey had shown. Instead he claimed that the blood kept the heart in motion, as a stream moves the wheel of a water mill. In
Riolan's view, blood prevented the heart from drying out, while the heart reheated the blood and replenished it with spirits. Although Riolan agreed with Harvey about that function of the heart, he contradicted him in insisting on the primacy of the liver.
Descartes's theory was closer than Riolan's to Harvey's. Thus Descartes accepted the full circulation of the blood through the body, but he rejected Harvey's theory of the motion of the heart. Arguing that physiological phenomena resulted from chemical processes, Descartes claimed that when the wet blood reached the hot heart it vaporized and expanded. This stretched the heart. As the blood cooled, it condensed, and the heart contracted. This alternate vaporizing and condensation accounted, in Descartes's system, for the heartbeat and pulse.
Both Descartes and Riolan agreed with Harvey that there were anastomoses connecting the arteries to the veins. Descartes incorrectly gave Harvey credit for discovering them, although Harvey had simply assumed they existed. Descartes accurately summarized three of Harvey's proofs for the circulation, namely the argument from ligation, the argument from the function of valves in the veins, and the fact that all blood in the body can exit from one cut artery. But he did not stress Harvey's estimate of the amount of blood that passes through the heart in an hour. Like Harvey and Riolan, Descartes believed that circulating blood carried heat and nutrition to the body. Like Harvey, he argued that blood was not itself a nutriment but carried food. In order to explain how the body obtained this food, Descartes drew on an analogy with sieves, which permit small particles to pass but retain larger ones. Descartes believed the heart repaired and renewed the blood. To explain the motion of the heart, Harvey and Riolan cited mechanical models — a pump and a mill — while Descartes, the mechanist, derived his explanation from chemical processes.
Harvey first published his theory in De motu cordis in 1628. It quickly found defenders and detractors in France. Although it was banned from the Parisian medical school, lecturers at the Jardin royal disseminated the theory, and by the 1660s a Harveian school had established itself in France, counting among its members Claude Tardy, Jean Pecquet, Jacques Mentel, Pierre Guiffart, Jean Martet, Jacques Chaillou, and Pierre Betbeder. Several defended the Harveian theory of circulation in vernacular treatises about such topics as the lacteal veins, the lymphatic vessels, chyle, and the preparation of blood. Their affiliations reveal that medical faculties had become receptive to the theory of circulation and that even physicians educated by faculties hostile to the theory might adopt it. Tardy was physician to the duke of Orléans and doctor regent at the Parisian medical
faculty. Chaillou practiced medicine at Angers. Martet was a master surgeon and royal anatomist in the faculty of medicine at Montpellier. Mentel had been educated in medicine at Paris in the late 1620s and early 1630s. Pecquet corresponded with Harvey and became one of the original members of the Academy. Most of Harvey's defenders published in the vernacular, perhaps hoping, as Guiffart put it, to reach a less dogmatic audience. Harvey's French proponents stressed his quantitative findings (although they gave different figures) and his experiments with ligatures, but they relied far less on analogies to explain the theory than had Harvey.
Analogical Reasoning in the Harveian Model
Harvey prefaced his De motu cordis with a plea for analogical reasoning. Indeed, in developing his theory in De motu cordis and De circulatione sanguinis, he discussed about a dozen analogies, using most of them to support his own theory. Some analogies he borrowed from the Greeks, some from political theory. Some were biological, and some were mechanical.
Harvey indulged in lazy or macrocosmic analogy only twice. In one case he made the commonplace observation that circularity is a natural phenomenon, citing Aristotle's view that "the air and rain emulate the circular movement of the heavenly bodies," that the condensation and evaporation cycle is a kind of meteorological circularity, and that the sun's circular motions cause storms. Harvey's purpose here was to justify a loose use of the terms "circle," "circularity," and "circulation." Moving from the truly circular revolutions of heavenly bodies — Harvey was no Keplerian — to the figurative circularity of the condensation-evaporation cycle, Harvey suggested that in this figurative sense, repetition constitutes circularity, which is thus akin to rejuvenation.
The second instance of macrocosmic analogy evolved into a biological analogy. Harvey wanted to show that "blood permeates from the right ventricle of the heart through the parenchyma of the lungs into the vein-like artery and the left ventricle." To show that such a passage is possible in nature, Harvey reminded the reader that water seeping through the earth "gives rise to streams and springs." Two other examples — sweat passing "through the skin" and urine "through the parenchyma of the kidneys" — show that Harvey employed a lazy analogy to demonstrate the general possibility of seepage in nature. But he chose a biological comparison with sweat and urine to illustrate seepage in the body.
A clearer instance of causal biological analogy exists in Harvey's explanation of the two motions of the heart, which "occur successively but so harmoniously and rhythmically that both [appear to] happen together and only one movement can be seen." He cited three analogies. Two were technological (involving comparisons with geared machinery and flint-lock firearms). The third and most extended comparison was with swallowing, and Harvey used this biological analogy to make his causal point.
Harvey anticipated later seventeenth-century biologists in taking "as a model of the living thing the living thing itself." He did not hesitate, however, to use mechanical models — such as the pump, the glove, and the filling of leather bottles — to draw causal inferences, starting from the premise that similar motions have similar causes. Thus, in careful hands even technological models could serve as causal analogies for the biological sciences.
Harvey's analogies reveal various causal assumptions and traits of argument. First, he explained biological processes chemically. Second, several models, such as the image of the "carefully planned and ingenious arrangement of ropes on a ship," were solely didactic. Third, in scrutinizing the analogies of his opponents, Harvey demanded rigorously close comparisons, pushing the analogies of others to their limits and ridiculing inept comparisons (like the notion that blood flows like water in the seas) by reductio ad absurdum.
In summary, Harvey used analogies in three ways. He proved that a process (such as permeation) was possible in one structure because it was already known in another. He taught by likening a phenomenon to a more familiar sight (such as a gun, a machine, or the ropes on a ship) whose workings were either well known or obvious to the observer. Finally, he justified the loose use of the word "circulate." Reasoning from macrocosmic models was relatively insignificant for his argument. While Harvey demanded that his opponents' analogies be accurate with respect to both behavior and causation, his own models were principally a source of general inspiration or a means of teaching. Whether heuristic or explanatory, they came mostly from outside the biological sciences. His causal analogies (the comparisons with swallowing, the leather bottle, the glove, or the fermentation of wine) simply assumed that similar phenomena resembled one another because they had similar causes. Finally, Harvey's analogical reasoning was not systematic but rather ad hoc or episodic. Thus, analogy rarely inspired him to apply either the methods or theories of another discipline to his own; it was unusual that likening the heart to a
pump led him to measure the flow of blood through the body or that chemical comparisons led him to draw theoretical inferences.
Harvey's theory of circulation unified the heart, veins, and arteries in a single system. He believed that his theory had utilitarian implications and could explain some "events fundamental in practical medicine," such as "the suppression or cause of hemorrhage, sloughing and gangrene, the assistance derived from ligature in castration or the removal of tumours." The explanatory power of the theory encouraged Harvey and his proponents to use it also to improve general knowledge of physiology, both animal and vegetable. His work offered more than a theory to botanists; it was also a model of experimental method and analogical reasoning.
By the 1660s the idea that blood circulates was well established in France, save in a few ultra-conservative circles. Although Harvey's theory had triumphed, it remained controversial and some savants were loyal to the competing views of Riolan and Descartes. Circulatory theory depended principally on observation, quantitative analysis, and an assumption that structure and function were closely related. But it was also indebted for its inspiration and exposition to analogical reasoning. It was only reasonable, therefore, for natural philosophers to apply circulation theory to plant physiology. While German and English savants were the first to raise the possibility, the French academicians soon surpassed them by testing systematically how well the model applied to the vegetable kingdom.
The hypothesis that sap circulates in plants just as blood circulates in animals was not the first attempt to liken plants to animals. Animals had served as models for explaining plants since ancient times, and seventeenth-century savants equated seeds to eggs, named the parts of plants after the parts of animals, and compared the structures of plants and animals. Such ideas became productive in the late seventeenth century, however, because botanists relinquished the Aristotelian distinction between animal and vegetative souls, which separated flora and fauna into separate causal categories, and because they sought causal mechanisms instead of causative "faculties." What had formerly been lazy analogical thought that merely affirmed the unity of living things became instead a guide to the empirical investigation of causal mechanisms. Thus, Harvey's theory reanimated botany at the end of the seventeenth century because it offered a heuristic model: it suggested experiments and practical applications that might ensue from a transplanted theory, and it stimulated the search for a causal mechanism.
The Circulation of the Sap
In the summer of 1668 Claude Perrault and Edme Mariotte defended the hypothesis that sap circulates in plants as blood does in animals. They identified five ways in which plants resemble animals: plants have two sorts of vessels, corresponding to veins and arteries; there are two sorts of sap,
and these are the equivalents of venous and arterial blood; sap is nutritious for the plant, just as blood nourishes the animal; the root manufactures sap just as the liver produces blood; and sap circulates frequently and quickly through the plant, replenishing itself with water from the leaves and being recooked in the root, just as blood circulates and is refreshed during its circuit through the body. Like Harvey, they had a hierarchical concept of the organism and emphasized "the control and stewardship" of one part of the body over the others, and like Riolan they incorporated traditional physiology — for example, the idea that the blood was itself a nutriment — into their theory.
The debate that the Academy sponsored marks the first systematic effort to apply circulatory theory to plants. Similar ideas were current outside the Academy in the 166Os: Johann Daniel Major had suggested the analogy, Timothy Clark had written about a circulation of the liquid in sensitive plants and had searched with a microscope for structural equivalents of valves, and Nicaise Le Febvre had compared the functions of sap and blood. In the 1670s and 1680s Nehemiah Grew and Marcello Malpighi impressed the botanical world with their systematic studies of plant anatomy and physiology. But it was Mariotte and Perrault who first pushed the analogy between blood and sap to its limits.
The debate of 1668 represents one of the Academy's most productive efforts at refereeing research. It began with the conflicting claims of Mariotte and Perrault for priority, and ended amicably by recognizing that their independent judgments had coincided. The exchange of evidence and opinions in 1668 influenced not only the two protagonists but also Duclos. Originally drawn into the debate to review the evidence, Duclos opposed the theory during the summer of 1668 but supported it in 1680. Finally, Perrault, Mariotte, and Duclos published their views about the theory.
The essential scientific traits of Perrault and Mariotte are exemplified by their work on the circulation of sap. Perrault was theoretical. He conjectured, offered plausible arguments, and identified the need for experimental support. In citing experiments, however, he rarely used the first person, and all the experiments cited in his 1680 book were actually performed by Mariotte, Huygens, Duclos, and Bourdelin at the Academy, not by Perrault himself. In contrast, Mariotte was emphatically experimental, and even his initial inspiration that sap circulates was prompted by an experiment.
Proving the circulatory hypothesis required academicians to address the three issues that Hesse has identified as crucial. Academicians had to establish the pretheoretic similarities between plants and animals that would make the analogy materially plausible; here they relied on lazy
analogies and on a functional resemblance. Next they had to push the analogy to its limits, testing for traits in plants that would correspond to those in animals; here academicians identified crucial dissimilarities that ruled out the relations of causality they originally anticipated. Finally, they were faced with the problem of crucial dissimilarities: plants were not comparable to animals in several significant respects, and in particular they lacked any internal motive force that could pump the sap as the heart pumped the blood. Because this latter dissimilarity could not be resolved, the analogy as a whole failed, and Mariotte and Perrault were left with a most difficult and important botanical question: how does sap rise in the first place? For an answer they turned ultimately to disciplines other than botany or zoology.
Botanists in the Academy first had to show that the circulation of sap was plausible. Like Harvey, who reminded his readers of other circular motions in nature and claimed "as much right to call this movement of the blood circular as Aristotle had to say that the air and water emulate the circular motion of the heavenly bodies," Perrault compared the circulation of sap to the cycle of condensation and evaporation. Harvey and Perrault both dwelt on the differences between living creatures and other things, Harvey stressing the connection between heat and life, Perrault the "natural connections" that unite the various parts of the body. Mariotte emphasized another of Harvey's themes, the connection between movement and life. Harvey affirmed that motion is necessary to generate the heat that is associated with life and pointed out that blood clots when it does not move, and Mariotte observed that still liquids stagnate and become corrupt or death-like.
Pretheoretic analogy or plausibility rested here on lazy analogy. Plants and animals were living creatures that depended for life on the motion of liquids that transported vital heat to all their parts. These were seventeenth-century truisms about the nature of life. Better pretheoretic support came from the specific context in which circulation of the sap was proposed. Perrault and Mariotte believed that this was above all a question of nutrition.
In 1667 Perrault had introduced the theory of circulation as a way of explaining how plants are nourished. In the following year he cast his entire analysis in the context of whether plants and animals are nourished similarly. When Mariotte explained what aspects of blood he meant to compare with sap, he started with the reception of chyle by the lacteal veins in the
mesentery and their transmission of this food to the venous blood. Following this non-Harveian interpretation of the lacteal veins, Mariotte described the full circuit of the blood and then a hypothetical circuit of the sap:
Probably the ends of the roots imbibe liquid from the earth and carry it into the body of the root. From there it passes into small vessels in the stem; and then it is distributed to the branches and ends of the leaves. The remainder is carried along different small channels to the root to be perfected by a type of cohobation and in order to become a well-digested sap, appropriate for the nourishment of flowers and fruits.
When Mariotte published the theory, he called his treatise "On the Vegetation of Plants," and he embedded the circulatory theory in a broader discussion of the chemical composition of plants, their germination and growth, the origins of vegetable nutrients, and the effects of plants on other living creatures.
These were the general grounds on which circular motion of sap was plausible. In addition to the vague principle that motion is necessary to generate life-sustaining functions, academicians cited the more specific need for nourishment characteristic of all plants and animals. A functional rather than a formal resemblance between plants and animals stimulated the analogy. But to confirm it Mariotte and Perrault still had to show that sap actually circulated and to find structures in plants that resembled the circulatory organs of animals.
Pushing the Analogy to Its Limits
Academicians sought to prove that sap circulated, first, by showing that their general theory of growth necessitated circulation and, second, by developing experimental evidence that demonstrated the descent of sap. Scientists at the end of the seventeenth century explained growth mechanically as resulting from the pressure of blood or sap against vessels in the extremities of animals and plants. That is why, explained Perrault, the French use the word "pousser" to speak of growth. Since all parts of plants and animals grow larger, all must be subject to this pressure. From a mechanistic theory of growth, it followed that sap must push downward as well as upward, because roots and the tops of plants grew, downwards and upwards respectively, in proportion to one another.
Experimental evidence for circulation was sought in several ways. Everyone assumed that sap rose from the root to the top of the plant. The
novelty was in showing that it descended again to the root. In 1668 Mariotte had already performed most of the experiments that proved descent of sap from the tops of plants toward the roots. He cut stems and observed that sap flowed in both directions. When he planted seeds upside-down, or placed them with the leaf-end in water and the root-end exposed above the water, the seeds grew. When he cut the filaments on roots, they bled. Uprooted chives, placed in water with only the shoots immersed, survived and grew for a fortnight. Most of the early experiments immersed seeds, plants, or parts of plants upside-down in water. Usually the plant survived and grew for several days. From these experiments, Mariotte and Perrault concluded that sap did move toward the root, that they had found two kinds of sap (yellowish and whitish in color, or thick or thin in consistency) in most plants, and that leaves could absorb water. Proving experimentally that sap descends to the root hence led to a promising observation, that there were two kinds of sap, and to an unforeseen consequence, that leaves had an important role in the nutrition of plants.
If leaves could absorb food, they endangered the analogy with animals, because an animal ingested food through a single mouth. Mariotte tested leaves in water and observed the sap in their branches. He concluded that leaves not only absorbed water but also carried more water than did the root to the vessels containing yellow sap. He also noticed that drops of water formed on the leaves of plants under a glass bell. Assuming that these were dewdrops, seeing that the plants remained healthy, and believing that no other water was available to the plants, Mariotte concluded that the leaves absorbed enough water to sustain the plant. Mariotte, the experimentalist, showed that plants, unlike animals, could take their food through two orifices. Perrault, the theoretician, tried to reconcile the new evidence to the analogy with animals. Here Harvey's own theory offered an explanatory model, for he had noted that medicaments applied externally to one part of the body entered the bloodstream and traveled to the entire body. Perrault, therefore, suggested that leaves absorbed liquids the way the skin of a dog absorbs the heat of a fire, or the skin of a butcher the fat of the meats he is handling. Mariotte affirmed the consequences of the experiments, while Perrault drew on folk wisdom and lazy analogy to reconcile the behavior of plants and animals.
If the descent of sap proved the circulation of sap, the existence of two kinds of sap in a plant provided another likeness between blood and sap. Harvey had shown that there were two kinds of blood: one, going out to the body from the heart, that was "hotter, perfect, vaporous, spirituous and, so to speak, nutritious," and one whose nourishment and heat were exhausted
and which returned to the heart "cooled, coagulated, and … figuratively worn out." For sap to be comparable to blood, therefore, rising sap should nourish and falling sap be weak and useless. Perrault asked whether there was a thick sap equivalent to arterial blood and a watery sap equivalent to venous blood, and Mariotte found plants that contained two different saps, yellow or white, thick or thin. The difficulty was to show that one was more nutritious than the other. Citing trees tapped for their sap in the spring, Perrault argued that falling sap cannot be nutritious, or trees would die from the loss of so much of it. Academicians analyzed the saps chemically but could not agree on the results. Although academicians compared the two sorts of sap with venous and arterial blood, they asserted resemblances more effectively than they proved them.
The analogy also constrained academicians to find separate vessels for carrying sap up and down the plant. In 1668 Mariotte could not determine whether there were two kinds of vessels. Perhaps mindful of Harvey's insistence to Riolan that one vessel could not accommodate simultaneously the flow of two liquids in opposite directions, Mariotte inferred from the two kinds of sap that there must be two sorts of vessels. Perrault, on the contrary, defended Riolan's stance, and tried to show by analogy that a vessel might permit both upward and downward flow, if the two liquids were sufficiently different. By 1679, Mariotte had studied the anatomy of plants more systematically and with a magnifying glass. He described the appearance of stems and the arrangement of fibers, channels, and spongy matter in them. But he still could not positively identify different vessels for different saps. In 1680, Perrault argued from Mariotte's 1668 experiments and from general information about trees that some plants had separate vessels and were therefore like "perfect" or higher animals. But he cautioned that the absence of separate vessels could not disprove circulation. Some plants were like insects, which do not have separate vessels. Perrault argued that the parts of plants must be able to differentiate cooked from raw sap, perhaps because of the disposition of their pores; in other plants the double bark or the bark and the pith might serve as separate conduits for different saps.
Equally serious was the lack of a mechanism for controlling the direction of flow. Mariotte and Perrault were uncertain whether they could identify valves or equivalents that prevented the rising sap from falling prematurely. Among academicians, La Hire agreed with Robert Hooke's sentiment that valves seemed "very necessary for conveying the juice of trees up to the height of sometimes 200, 300, and more feet; which he saw not how it was possible to be performed without valves as well as motion." La
Hire claimed to have found valves in canes and reeds. Allowing expectation to prejudice observation, he argued from similarity of function to resemblance of structure and insisted that he had found valves where none existed.
Skepticism about the existence of valves or separate conduits required academicians to consider whether sap flowed in different directions in the same vessel. Grew believed this was so. Perrault tried to explain that it was possible by using an analogy with water vapor, which can rise through oiled paper but cannot penetrate it again once the vapor has condensed. He offered a second analogy, with two sponges, one soaked in water and the other in oil, each of which absorbed liquid of its own type when placed in a mixture of oil and water. Both arguments presumed that the parts of plants were designed to accept one kind of sap and reject the other.
Each structural comparison endangered the analogy. The closest resemblance was between blood and sap, liquids that were of two kinds and that made a complete circuit of the body in question. Organs and blood vessels, however, challenged the ingenuity of savants. Academicians tried to compare the root to the heart, the soil in which a plant stood to the intestines, but even with a microscope they could not identify two distinct sets of vessels. The most serious difficulty, however, was that since plants lacked a heart, they had no pump to drive the sap.
Solving the Problem of Crucial Dissimilarities
Failure to find equivalent organs weakened the analogy seriously. The absence of what Hesse calls horizontal analogues meant that the causal mechanism was missing in plants. Academicians were reluctant to discard the circulatory hypothesis altogether, once they had found evidence that sap descends. But purported equivalents, putative valves, and two-way vessels were inadequate to explain the principal problem of the circulatory analogy, the very issue Perrault had identified with his opening words in 1668: how does sap rise in the first place?
One escape from the failed analogy was to compare plants with "lower" animals, whose anatomical organization was less differentiated. Such a move was consistent with the Harveian model, for Harvey had noted that valves are "not present in all animals" and are not "made with equal skill in all the animals in which they are present." Harvey had also allowed for circulation in animals that lacked hearts, and plants seemed similar to what Harvey had called "plant-animals." These were creatures such as oysters
and earthworms, which had only rudimentary hearts or no hearts at all, because they were too small, too cold, too soft, and "too little differentiated in their structure." Harvey admitted that they did not need "a propulsive organ to transmit food to their extremities." Their bodies were limbless and homogeneous. In them, ingestion "and expulsion of food is an in and out movement produced by contraction and relaxation of the body as a whole." They need no heart because "they use the whole of the body as such and an animal of this sort is in effect nothing but a heart."
Valveless veins and heartless creatures, therefore, offered two escape routes to scientists who used Harvey's theory as a model for plants. A heart, valved veins, and pulsating arteries were not necessary for circulation in all animals, since the entire organism might serve as a propulsive mechanism, driving nutrients and excrement through itself. But plants differed from the plant-animals: they tended to be larger, had a more differentiated structure, and were stationary. Botanists who took the view that the entire plant could propel the sap upward would have to look for an external motive force. To show how sap rose at all, therefore, academicians had to look beyond anatomical or structural identities. They had to seek nonbiological forces operating outside or within the plant. Botanists still sought a pump, not organic but figurative, that could impel sap in a direction contrary to its natural downward flow.
In the absence of a biological causal mechanism, academicians turned to two explanatory modes: chemical and physical. The former operated inside the plant and was part of the normal physiology of a living creature. The latter could be either external or internal, depending on what kind of phenomenon was cited. Chemical explanation was consistent with the Harveian model, for the digestion of nutrients was thought to be a chemical process that resulted in effervescence and rarefaction of the digested substances. The physical explanation, on the contrary, relied on concepts of air pressure and capillary action unknown to Harvey. Both chemical and physical mechanisms were invoked by Perrault and Mariotte, who thereby diluted the biological model with nonbiological explanatory mechanisms. But the physical model itself was uncertain, since scientists in the late seventeenth century were unclear about the causes of capillary action. Thus the analogy with the circulation of blood, which had a visible and organic causal mechanism, led botanists to adopt as a causal mechanism a mysterious phenomenon that had only recently been investigated. When the analogy between the motions of blood and sap could not be sustained, academicians related the rise of sap to capillary action and air pressure.
When those explanations seemed inadequate they cited the chemical phenomena of effervescence and rarefaction.
Explaining the Rise of Sap
The concept of capillary action was regarded as novel during the 1660s. Robert Hooke believed the phenomenon had first been observed by French scientists:
An Eminent mathematician told me one day, that some inquisitive Frenchmen (whose Names I know not) had observed, that in case one end of a slender and perforated Pipe of Glass, … be dipt in water, … the liquor will ascend to some height in the Pipe … tho held perpendicular to the plain of water. And to satisfie me, that he mis-related not the Experiment he soon after brought two or three small Pipes of Glass, which gave me the opportunity of trying it.
Robert Boyle experimented with capillary tubes in 1660, discussed capillary action in 1671 and 1676, and tried to measure the force of capillary imbibition in a seed. Huygens knew of his work, saw demonstrations of capillary action at Rohault's house in December 1660, and attended a meeting at Gresham College in April 1661 where the phenomenon was discussed; he also owned a copy of "Boyle's article on the rise of water in small tubes and on other phenomena which we call capillary."
Capillary action seemed to seventeenth-century scientists to explain several natural phenomena. Hooke listed these effects of capillary action:
… the Rising of Liquors in a Filtre, the rising of Spirit of Wine, Oyl, Melted Tallow, & c. in the Weake of a Lamp (tho made of small wire, threeds of Asbestus, Strings of Glass, or the like) the Rising of Liquors in a Spunge, piece of Bread, perhaps also the ascending of Sap in Trees and Plants, through their small, and some of them imperceptible Pores, (of which perhaps I may say more on another occasion) at least the passing of it out of the earth into their roots.
He believed that capillary action was the result of unequal air pressure, with the air pressing heavier on the reservoir of water surrounding the thin glass tube than on that within the tube itself. Hooke reiterated the view in 1665 and stated that air pressure caused sap to rise in plants, basing his explanation on the analogy with capillary action. This confusion between capillary action and the effects of air pressure persisted throughout the century, despite G. A. Borelli's argument in 1670 that capillary action was not due to air pressure.
Because capillary tubes resembled the stems and vessels of plants, they were an obvious model. In the late 1670s Mariotte and La Hire used the analogy between glass tubes and the vessels of plants to explain how sap rose. Mariotte limited the effect of capillary action, however, to "the first entry of the water into the roots." This, he said "occurs by a law of nature similar to the movement of union of which I have already spoken; since whenever very narrow tubes touch water, it enters, and it even rises despite its natural tendency to descend." For capillary action to work in plants, three conditions had to exist: the water in the soil had to touch the plant, it had to have access to that part of the plant in which it could rise, and something had to cause the liquid to enter and rise in the plant. Mere contiguity seemed to be insufficient because if a glass tube were dirty or rubbed with tallow, water would not rise in it. Furthermore, the pores of plants had to be properly "disposed to allow the subtle parts of other bodies to enter." Finally, these subtle parts had to "be pushed by some principle of motion." This principle Mariotte referred to as "a movement of union" and as an effect "that is popularly called attraction"; he did not cite the pressure of air as Hooke had done.
But there were problems inherent in comparing the rise of sap in plants to the rise of liquids in capillary tubes: the cause of capillary action was disputed and liquids did not rise so high in capillary tubes as they did in plants. Thus, whether or not capillary action was cited, savants turned to air pressure in order to explain the rise of sap in taller plants.
Huygens initially favored the view that sap rose because of air pressure, and in 1668 Perrault propounded an explanation that depended on multiple causes, including air pressure. The theory that air pressure causes sap to rise was known to be defective, however, by 1679. Pierre Perrault and Huygens debated whether sap rose because of air pressure, as Huygens maintained, or because of attraction and nature's abhorrence of a vacuum, Perrault's view. Perrault cited the following as a decisive argument against Huygens's theory:
How can we understand the sap that rises in trees? Can one say that air pressure causes it to rise between the bark and the wood, as in a pump? For that it would be necessary for the foot of the tree to rest in a reservoir of sap. Even if that were the case, this sap could rise only thirty-two feet, but there are trees that are more than one hundred and twenty feet tall.
Pierre Perrault concluded that sap rose as a result of "attraction due to abhorrence of the void," a phrase that he and Mariotte used apologetically
and as a manner of speaking not intended to impute emotions to inanimate or mechanical objects.
Since neither capillarity nor air pressure seemed sufficient to raise sap higher than thirty feet, some savants adduced chemical reactions inside the plant. Claude Perrault had argued all along that sap rose for many reasons, including the existence of appropriate passages in the plant, air pressure, external propulsion from the wind, and coction of sap. Influenced by his brother's objections, however, he modified this view when he published his Circulation in 1680. There he cited both air pressure and attraction due to fear of the void, but he also elaborated in Cartesian fashion his earlier chemical explanation: when sap was prepared, fermentation and effervescence reduced its concentration so that more sap rushed in to fill the potential void. To show that sap would flow into an area of diminished pressure within a plant, Perrault cited the effects of an air pump: "plants that are full of sap let it run when the air is being evacuated, and when the pressure of the air is diminished, the sap dilates and becomes less condensed than it was." Mariotte developed a slightly different theory in 1681: sunlight evaporated sap in the upper regions of the plant, creating an area of lower pressure into which sap rose. Such formulations anticipated Hales's conjecture that the loss of liquid due to transpiration pulled sap upward, continuing a process begun by capillary action.
Tournefort presented a different eclectic theory in 1691. He believed he had found two different systems in plants, one in which sap rose by absorption and another in which it rose by capillary action. The vessels in most plants, he said, were soft, spongy, and composed of many small, empty bladders or pouches that were connected so that sap passed through them. He compared them to felt strips or cotton that filtered and conducted liquids. Not all vessels were spongy, however; the stems of water-plants were like cylinders pierced longitudinally with holes. These tubes carried sap, and Tournefort thought they resembled capillary tubes: "this structure seems to favor the sentiment of some natural philosophers who believe that the sap ascends in plants for the same reason that water rises in very narrow glass tubes." Tournefort followed G. A. Borelli, who claimed that the dilation and condensation of air enclosed in plants caused sap to rise and that the spongy matter in plants facilitated that rise. La Hire, however, challenged the Borelli-Tournefort hypothesis after observing that water did not rise significantly in absorbent materials such as sponges inserted in glass tubes or paper strips. The best result was a height of 225 lignes over a period of more than eighty-four days. La Hire concluded that neither absorbent matter nor capillary action could account for the rise of sap.
Instead, he maintained that only hollow tubes in plants could transport sap, and he claimed to have found hinged, woody valves in them that enabled sap to rise.
The problem of how sap rose elicited varied responses from academicians. Huygens proposed air pressure, while Perrault listed several interrelated causes, such as air pressure, wind, fermentation, and the different weights of raw and cooked sap. Once air pressure was ruled out as a sufficient cause, Mariotte and La Hire focused on capillary action, while Tournefort combined capillary action with a Borellian theory about spongy matter in plants. Later, La Hire adopted the view that the vessels of plants were valved. In each case, academicians used analogies. Since the biological model of valves was inapplicable, they drew mostly on chemical or physical explanations. But the limitations of all models forced most academicians to develop theories based on multiple causation.
Academicians used the hypothesis of a circulation of sap to search for causal mechanisms. By choosing the Harveian model botanists tried to replace the two principal modes of explaining living things — chemical and mechanical — with a biological one. When the analogy failed, academicians had three choices. They could force a biological explanation by insisting on false structural resemblances. They could fall back on either or both of the traditional modes of explanation. Or they could draw on new physical models that were only half understood. Since the Harveian model itself assumed chemical processes within the physiological and retained a technological model for the heart, recourse to nonbiological explanation was broadly consistent with the model.
Circulatory theory had both substantive and methodological shortcomings. Although a circuit of sap was established, structural resemblances alone between plants and animals could not justify a causal analogue. The effort at methodological equivalence fared no better, despite the experimental ingenuity displayed by Mariotte and La Hire, whose demonstrations of the direction of flow sometimes resemble Harvey's tests. Harvey's crucial experiments were done on living creatures, however, and his theory owed a great debt to his skill at vivisection, but all of Mariotte's and La Hire's dissections were of dead plants. Experiment is necessarily an artificial procedure that may distort its object, and it is least informative when it examines defunct organisms in order to understand physiological processes.
Given these failures of the analogy, did it have any value at all for seventeenth-century botanists? First, the circulatory analogy had useful consequences despite being a weak form of a partially failed induction. In the absence of a compelling alternative, botanists found a partial analogy better than none at all. Although the causal resemblance failed, a circuit of sap was established. By calling that a circulation, botanists implied that plants enjoyed the digestive and perfecting processes characteristic of animal nutrition. While the circulation of sap could not be subsumed under the laws governing the circulation of blood, the term "circulation" reminded botanists of both the circuit and its function, if not its causal mechanism. Hence, the analogy with the movement of blood supplied a suggestive language to botanists, who retained some of the connotations that the word "circulation" had grown to have for natural philosophers.
Second, because academicians used the experimental and observational form of analogy, their analogy was both positively and negatively useful. It aided "the investigation of structure and the relation of structure and function" and helped reveal some "properties hitherto unnoticed." It also led academicians to ask new questions and to propose different causes, causes that were testable. Because the extension of the metaphor was more limited structurally than had been foreseen, however, botanical investigation did not affect notions about the physiologies of animals or "plant-animals." Finally, those who did not insist on putative valves in plant vessels learned from the circulatory analogy that there was no organ in plants to make sap rise.
Third, when a model cannot lend its mechanism because of structural disanalogies, the principal value of analogical reasoning must be as an inducement to comparative method. In the case of plants and animals, this may be inevitable, for the two types of organisms enjoy similar functions but dissimilar structures. Analogies used experimentally can draw attention to these problems. But for analogy to work as comparative method, the researcher must not assume the identity of the two things being compared. Therefore, an analogical argument must start by elucidating similarities and differences, as Hesse has pointed out. In this case, the analogy with animals forced botanists to ask how plants accomplish certain functions without having the appropriate organs. By retaining the analogy while admitting structural dissimilarity, academicians moved from analogical to comparative method. That is, they used the analogy to locate specific resemblances and differences; they then tried to explain the differences by comparing the causal mechanisms of the two. In the case of the Academy's study of sap, this transition was incomplete. Some academicians
persisted in pressing the structural comparison by searching for valves. No one seems to have questioned the functional analogy at all, so that the physiology of plant and animal nutrition was assumed rather than tested.
Academicians simultaneously escaped from and succumbed to the dangers of analogy. Although they experimented and acknowledged numerous and crucial dissimilarities, they also assumed fundamental resemblances without examining them. In matters of nutrition, analogy did substitute for experiment. Moreover, when La Hire was driven to find nonexistent valves, he let the model become axiomatic.
The Academy's circulatory analogy could be disproved by experiment and observation. Unlike Harvey's own analogies, which were didactic or were instances of similarity chosen to promote general plausibility, the analogy between sap and blood was falsified by significant dissimilarities. As Canguilhem has pointed out:
A good hypothesis is not always that which leads rapidly to its own confirmation, … It is that which obliges the researcher, by dint of an unforeseen discord between the explanation and the description, either to correct the description or to reconstruct the schema of explanation.… [I]n biology the models which have the chance of being the best are those which halt our latent tendency to identify the organic with its model[.]
The hypothesis of the circulation of sap had merit in drawing attention to a central problem in botany, namely, how sap rose at all.
It further represents an early attempt to use biology itself as a model for biological explanation. Academicians helped transform botany by finding new explanatory models. But when the biological model failed to supply a causal mechanism, academicians resorted to nonbiological causes, a fruitful reliance that affirmed the interdisciplinary character of scientific explanation. It was not "the impossibility of explaining how the vegetable machine works solely by the laws of motion" that drove botanists to zoology for inspiration. Rather an incomplete correlation between the zoological model and the vegetable explicandum forced savants back to nonbiological explanation. Seventeenth-century botanists and anatomists found that mechanics, physics, and chemistry were necessary weapons in their explanatory armory. Far from demonstrating a failure of self-image in the biological sciences, the resort to chemistry and physics exemplifies the cross-disciplinary fertilization so important for early modern science, whose practitioners were adept in many fields. Moreover, it reveals a nondogmatic use of analogy. Academicians proved some resemblances but also identified crucial dissimilarities that led them to identify an important scientific problem whose solution lay outside the original analogy. In so doing, they transformed analogical reasoning into comparative method.
Chemical and Mechanical Explanation of Physiological Processes
The seventeenth-century upheaval in natural philosophy meant that savants were embroiled in countless debates. They disputed theories and challenged evidence, and they disagreed about the order in which investigations should proceed. Although in principle academicians argued for completing natural historical research before addressing natural philosophical questions, in practice they could not wait. In botany, they sought principles that would account for the life cycle of a plant and turned to three forms of explanation: chemical, mechanical, and biological, with the biological model itself depending on chemical and mechanistic explanation. Chemistry was pivotal because it was susceptible to both mechanistic and vitalist interpretations; like botany it was in the throes of redefinition. Academicians were uncertain just how far they could reduce chemical processes to mechanical causes, and their eclectic accounts of plant physiology reflect their quandary.
Generation and Reproduction
Perhaps the most perplexing aspect of the life sciences during the seventeenth century was generation. The respective roles of female and male, the nature and function of eggs and spermatozoa, and the sexuality of plants were all at issue. When academicians considered the generation of plants, they focused primarily on determining which of two incompatible mechanistic theories — spontaneous generation or preformation — accounted
more plausibly for certain phenomena. According to the theory of spontaneous generation, animals and plants could be generated from soil, air, or corpuscles directly, without the need for progenitors of their own type. Preformationists held that living creatures carried within themselves perfectly formed descendants in miniature, so that the process of generation involved little more than giving birth to these entities. New experiments, observations with the latest instruments, and theological objections undermined both theories, however, and at the same time clarified the role of seeds in plants.
Perrault opened the Academy's discussion of germination and reproduction with his paper of January 1667; academicians subsequently studied seeds, earths, and the conditions for germination, examined vegetative reproduction, and debated preformationism. Always interested in testing the claims of the ancients, Perrault and Dodart were skeptical about Theophrastus's assertion that plants grew from their saps, and also about the contemporary chemical notion that salts extracted from plants acted as seeds. Other academicians emphasized reproduction by seeds and by vegetative propagation. Here the natural history complemented their natural philosophical research. The Marchants described the location and appearance of the seed, Bourdelin analyzed seeds chemically, and Homberg discussed their properties.
Most academicians were dubious about spontaneous generation. In 1667 Perrault suggested testing the theory by observing earth taken from so deep in the ground that seeds could not have penetrated there; this would determine whether plants could grow without seeds. In the 1690s Tournefort showed that it was best to assume plants had seeds; if seeds had not been seen, it was probably because they were small enough to elude observation. He identified them in several plants previously said to have been seedless, especially ferns. Examining with a microscope the dust-like dots on ferns, he saw that they were "tiny sacks, each of which contains a large quantity of seed." In one capsule Tournefort counted more than three hundred individual seeds, and he grew a fern from some of them. He opened capsules previously thought to be the seeds of Lunaria and Polypode and, using a microscope, showed that they too contained numerous tiny seeds. Where even he could not find seeds, Tournefort argued analogically: if a plant whose seed was unknown passed through the same stages of growth as a plant known to grow from seeds, then it was proper to infer that the first plant also grew from seeds. Thus Tournefort claimed that the maidenhair fern of Montpellier (capillaire de Montpellier ) grew from a seed,
because its shoots consisted of a leaf and a thin root, like those of other plants.
Although Tournefort described his own observations in the context of Grew's, Ray's, and Morison's discoveries, he criticized his English counterparts for stopping short of full discovery. He contradicted Morison, for example, who believed that mushrooms sprang directly from the earth. In a large fungus taken from the woodwork in the abbey house of Saint Germain, Tournefort identified as seeds some fine dust attached by delicate threads to the pores of the fungus. He then looked for their source, what he called the ovary of a plant, in the rough crust on the back of the mushroom but concluded that this could not be the ovary since there was no seed there. Since he believed that similar natural objects should display similar natural processes, Tournefort disagreed with Morison's explanation of why the fungus Erysimum was more common after the London fire of 1666. Morison claimed that the mushroom had grown spontaneously from soil that was altered by the fire, but Tournefort replied that changes in the soil simply encouraged the seeds to germinate.
Both Mariotte and Tournefort examined the mechanisms of seed dispersal, especially in plants like wood sorrel, dittany, wild cucumber, and others that threw their seeds great distances. Their shapes and appendages seemed to enhance propagation. Mariotte observed that the seed of a moss called rampion was slim and thus could slip through the dense growth to the ground. Tournefort believed the spiral shape of dittany seeds helped them spring away from the plant. Seeds were known to travel great distances, sometimes because their hooks and hairs attached to animals. Mariotte also described tip-layering and recalled that one of the Marchants had shown him a clover growing in the Jardin royal "whose flower, when it began to dry, curved and grew into the soil, so that the seed formed there and the clover in effect planted itself."
Driven by a Baconian quest for data and inspired by zoological models, academicians observed vegetative reproduction and checked their hypotheses experimentally. Above all, they used their findings to adjudicate between the theories of spontaneous generation and preformation, with the mechanists Mariotte and Tournefort on opposite sides.
The theory of spontaneous generation had a long pedigree stretching back to the ancient atomists. Although rejection of the theory has been heralded as a seventeenth-century contribution to modern science, some of the best minds continued to accept that plants and animals could be generated spontaneously. Mariotte, one of the principal experimentalists
of the Academy, argued that plants could be propagated when two or three corpuscles hooked together in the air, water, or earth. Such a union could "give the first impulse to [a plant's] growth," as for example when grass grew on the site of a dried pond where no seed could have fallen. Unlike Tournefort, who used circumstantial evidence to subsume the exceptional under a general inductive rule, Mariotte invoked a corpuscularian theory of matter to perpetuate the exceptional cases.
The theory of spontaneous generation waned in popularity during the seventeenth century, albeit more slowly among botanists than among zoologists. Thus discoveries concerning generation often became grist for the preformationist mill. Savants cited animalcules to refute spontaneous generation and to support preformation. Plants had long seemed to offer particularly strong evidence in favor of preformation, and here, exceptionally, an analogy from botany influenced the development of theoretical zoology.
Opinion in the Academy was split. At the end of the century, Tournefort and Dodart spoke for preformation. But Mariotte had earlier rejected it altogether after he, Dodart, and Jean Marchant studied bulbs of tulips, lilies, and narcissi in 1677 and 1678 without finding even one entire, mature plant in miniature. Mariotte concluded that the mature plant did not exist in either bulbs or seeds. Other evidence also seemed to disprove the theory: the knots on a rosebush produced flowers in the spring but branches and leaves in the autumn, and grafts might take three years to flower. Nor could preformationism account for variations within a type of plant: apple trees, pear trees, and melons were so varied that to accept the preformationist view — that one seed could contain an infinite number of identical plants — entailed making unpalatable assumptions, such as that one plant produced varied seeds or that plant families did not exist.
Mariotte repudiated preformation and also the related theory of emboîtement , which maintained that the parent organism contained its descendants, but that these were not perfectly formed. He argued instead that plants developed their parts and properties gradually, as the result of an interaction between the plant and its sap. Seeds contained "only the principal parts of plants" and all other parts were developed "in succession as a result of the way the first parts affected the sap." Mariotte concluded:
But it is not believable that this small composite of corpuscles contains all the branches of this Plant, its leaves, its fruits, and its seeds; and even less that in these seeds there could be contained in miniature all the branches, leaves, flowers, etc., of the Plants which will be produced ad infinitum after this first germination.
Like his contemporaries, Mariotte could not adopt both spontaneous generation and preformation (or emboîtement ); unlike most of them, his corpuscularian theory of matter predisposed him toward spontaneous generation.
Mariotte was the exception to a seventeenth-century trend. Most savants cited microscopic research to disestablish corpuscularian theories of generation in favor of preformation. Here observations, not alternative theories, were decisive. With the microscope, savants saw a new world of seeds, spermatozoa, ova, cells, and other objects previously unimagined. Finding seeds where earlier they had gone unsuspected helped dethrone spontaneous generation. But for Mariotte, corpuscularianism was too useful a theory to abandon. It even seemed to be confirmed by the microscope, which showed tiny particles, invisible to the naked eye, that might well be corpuscles. Because of his theoretical bias, Mariotte's microscope became a weapon not against spontaneous generation but against preformation. The microscope was important but not necessarily decisive. A savant assessed experimental evidence within a framework of theological or philosophical assumptions before choosing between theories. In Mariotte's case, theological objections to spontaneous generation were less persuasive than the philosophical merits of corpuscularianism.
Germination, Maturation, and the Role of External Factors
Zoology also inspired the Academy's experiments and theories about germination. Perrault recommended microscopic research to discover just how plants grew from seeds, and Dodart compared the Academy's studies of germination to studies of chicks in the egg. Although academicians never rivaled the detail of Grew's or even Samuel Foley's studies of the anatomy or development of germinating seeds, they claimed interesting analogies between plant and animal parts. Working with a germinating white bean squash and other seeds, Mariotte and Perrault described the filament connecting lobes to leaves as an umbilical cord. Mariotte also thought that seed lobes of beans, pumpkins, cucumbers, and melons resembled the yolk of an egg or the liver in being a source of food for the embryo plants.
Mariotte explained the process of germination mechanically:
It is thus probable that the principal parts of the germination of Plants are contained in their seeds, and that they are predisposed to form fibers and pores suitable for the filtration and the union of certain principles that pass there, as
if through channels or molds; from which the other parts are formed, such as fruits, seeds, and the beginnings of the second germination.
His mechanistic and analogical explanation challenged traditional views of savants like Duclos. Where Mariotte dismissed a vegetative soul in plants on the ground that no one had ever found one, Duclos preferred vegetative souls to analogies between the parts of plants and the organs of animals. Duclos thought plants and soil had similar natures; unlike his colleagues he did not differentiate the various parts of plants by their function, saying rather that all parts of plants (and of soils) contributed equally to germination and maturation.
Any account of germination had to weigh the roles of the plant itself and of external conditions such as sun, soil, air, and water. Perrault and Mariotte stressed the sun. Perrault conjectured that it cooked nutritious minerals in the rainwater. Mariotte demonstrated that sunlight was essential to the growth of plants by comparing seedlings grown under earthenware pots with seedlings grown under glass domes. He proposed two theories, one mechanical, the other chemical, to explain the sun's effect: either sunlight encouraged water to rise in the plant, and then water turned the plant green, or sunlight affected the chemical nutrients in the water.
Soil, air, and water seemed to be the most influential external conditions for germination and maturation. Local conditions could encourage or inhibit growth, and plants either depended passively on what they took from the soil or transformed it to suit their needs. Mariotte and Perrault discussed the nutrients plants required from the soil. Tournefort thought that the earth's juices were the single most important stimulus of germination. They were prepared in the soil by agitation, moisture, heat, or cold, and shaped by the air and the pores of soil through which they passed. Tournefort emphasized mechanical processes — motion, air pressure, the sieving effect of pores — but he also considered the chemical composition of soils.
Academicians studied earths systematically in the 1670s. In 1675 Dodart proposed several experiments. He planned to extract "the salts, and if possible, some other substances from the different kinds of earths." He hoped to distinguish soils chemically, to differentiate among the salts in soils, to discover a connection between salts found in the earth and the salts of plants that grew there, and to identify the different proportions of salts in the same soil under various conditions.
For Dodart and Borelly the purpose of research on earths was to understand what made soil fertile. But they could not persuade Bourdelin
to study soils according to the methods they preferred. From the end of 1675 until the end of 1677, Bourdelin analyzed marls, clays, and other kinds of soils, distilling them as usual in the retort, some with and others without the fixed salt of saltpeter. He calcinated the testes-mortes and then tested the liquids extracted for their reactions to chemical solutions, just as he did with the products of distilled plants. Bourdelin found that earths released liquid with a sulphurous odor, vitriolated salts, volatile salt, and oil; the teste-morte of one earth was said to taste like common salt.
Borelly promoted solvent analysis over distillation and objected to using the fixed salt of saltpeter in distilling earths. He and Dodart preferred lixiviating earths "in order to extract all the salt and all the various substances together in their chaos"; afterwards the earths could be rectified and purified so that their separate parts might be identified. Salts obtained thus could be used in numerous experiments. Any earth remaining after lixiviation could be tested further by solvents.
After Borelly criticized him, however, Bourdelin simply distilled fewer earths, while never adopting Borelly's method. Like the dispute over the relative merits of distillation and solvent analysis of plants, so the disagreement over the proper way of studying soils found Bourdelin and Borelly in opposition. Both disputes were resolved in Bourdelin's favor by his intransigence; Bourdelin would not abandon his preferred technique, despite the pressure exerted by his colleagues.
How Plants Grow and How They Are Nourished
Mariotte and Tournefort explained plant growth mechanically, Homberg chemically. Mariotte thought that as water evaporated, various "earthy, salty, and oily parts" remained to mix and unite with the plant, creating "the hardness and solidity of the branches." He argued that although plants could not select what they took from the soil, they could transform it and actually absorb more oil as they matured. For mechanists like Mariotte and Tournefort, the circulation of the sap caused growth by putting pressure on the extremities of the plant. Rising sap stretched plant cells, causing the cells and hence the plants to grow; when a cell could stretch no longer, the plant withered and died. Tournefort thought this theory also explained the maturation and release of seeds. Observing the organs of plants — the ovaries of hellebore, aconite, and crown imperial, the fruits of spiny poppy, false dittany, toothwort, and the pods of the plant Caspar Bauhin named Lathyrus latifolius — Tournefort found that plants
released their seeds when the fibers in the ovaries dried and contracted, and he argued that when the ovaries opened, air entered and helped the seeds ripen.
Homberg, however, used Bourdelin's analyses to develop chemical explanations of how seeds and plants grew. Homberg concentrated on the maturation of seeds. Noting that unripe seeds yielded a lot of water, less oil, but more fixed salt than ripe ones, Homberg gave this account of their development:
… the organs of the young seeds contain only a watery and very fluid sap, which is not yet well digested; after these salty, earthy, and watery parts have mixed together more perfectly over time, they thicken and create this oil that forms little by little.
To strengthen his claim, Homberg compared young seeds with ripe fruits, nuts, and olives; stored in a dry place for three or four months they too yielded more, and thicker, oil than when they were freshly plucked. Homberg reasoned that the young seed resembled ripe fruit and became oilier as it matured. He also distilled fetid oil with quicklime; this diminished the oil, changed its color, and produced a lot of water. Homberg argued that the phlegm, salt, and earthy matter of young seeds "together create over time the quantity of oil that is found in ripe seeds." He believed he had separated the oily compound into the simple substances out of which nature had formed it. When rectifying oil with quicklime, for example, the quicklime separated fixed salt and earth from the oil; thus, Homberg reasoned, the oil must consist of salt, water, and earth.
All academicians agreed that only chemical analysis could explain the origin and nature of plant nutrients. Boyle, Helmont, and others stressed water and deprecated soil as the source of nourishment, and academicians investigated the role of rainwater and dew in the growth of plants. But savants who did not accept Helmont's view that water was the ultimate source of matter had to identify the origin of the nutriments found in water. Academicians debated whether these came from the atmosphere or from the earth, a question that turned on salts.
For Mariotte and Perrault, nutrients came intermediately from the earth but ultimately from the atmosphere when sulphur, saltpeter, and volatile salts fell in rainwater to the ground. Duclos disagreed with his colleagues. In his view, the fertile "fatty and sulfurous salts" formed in the soil, not in the air. As proof he cited his analysis of the waters that condensed inside and outside a concave vessel placed on the ground: dew had more volatile salt than either the rainwater or the air vapors that collected on the outside. His
arguments convinced Perrault, who conceded that the nutrients originated in the soil from living or decayed plants and animals or from whatever produced mineral salts in well water. Perrault thought such nutrients were cooked by the sun when they rose in vapors.
Applying chemical analysis to a concept of the food chain, Homberg developed a theory about the different origins of the different salts. He noticed that most plants were composed of three salts: fixed lixivial salt, volatile urinous salt, and volatile acid salt. Bourdelin's analyses showed that fixed lixivial salts and volatile urinous salts occurred only in the distillants of plants, of herbivorous animals, or of animals that ate herbivorous animals. The third substance, volatile acid salt, was found in soils, including ones that had no vegetation, and in plants that grew in all kinds of soil. Volatile acid salts thus came from the earth. The other two salts — fixed lixivial and urinous volatile — were therefore manufactured in the plant.
The Academy was divided on whether seeds and plants were active or passive. Did they simply absorb juices already prepared in the earth or did they transform what they took from the earth? Tournefort took the passive view. He believed that juices altered in the earth and became more or less suitable to various plants. Mariotte, Perrault, Duclos, and Homberg took the contemporary view that seeds and plants changed what they took from the soil, but they disagreed about how this happened. Mariotte believed the liquid was simply a vehicle for minerals and that plants used the mineral residue only after the liquid had evaporated. Perrault and Duclos believed the plant transformed both liquid and minerals, and Duclos thought it did so by coagulation. Homberg believed plants imbibed one kind of salt from the earth but created two additional salts themselves.
Seventeenth-century botany was eclectic. Zoological anatomy and physiology lent it a vocabulary, an experimental repertoire, and some explanatory theories about physiological processes. Chemistry and mechanics accounted for generation and reproduction, germination and growth, and nutrition. Some academicians took these explanations as complementary, especially when they answered related but different questions. Thus, they might explain chemically how a plant assimilates nutrients and mechanically how a plant gets larger or dies. Mariotte, for example, cited both mechanistic and chemical theories in his discussions of plant physiology. Homberg and Tournefort, however, did not try to combine the theories — Homberg's primarily chemical, Tournefort's predominantly
mechanistic — that they presented separately but contemporaneously at meetings of the Academy. Nor did the Academy as a whole encourage them to unify their hypotheses into a general account of plants. Academicians never tried to develop a treatise on plant physiology that would rival either the detailed and original works of Grew and Malpighi or the derivative, systematic essays of Régis. The natural philosophy of plants was too tentative a discipline to justify a collaborative project similar to the natural history of plants.
The Academy as an institution never encouraged members to develop a comprehensive theory of plants, to resolve their inconsistent interpretations, or to explore the implications of their piecemeal observations and conclusions. Nevertheless, it aided the development and expression of their theories in three ways. First, the Academy offered a forum for discussing and publishing these early studies of plant physiology. Second, the Academy's natural historical research supported its natural philosophical inquiries. Studies of seeds, the cultivation of plants, and chemical analysis — all ingredients of the natural historical project — fed theories about reproduction, the conditions of germination, and maturation. The official project provided not only data but also protection for the hesitant and unofficial natural philosophical studies. As a result, collaboration on the failed natural history of plants bore fruit in individual studies of plant physiology, with chemical analysis, more than any other tool of research, connecting the two kinds of inquiry.
Third, the Academy's interdisciplinary composition and interests encouraged members to study plants with the new instruments. As the next chapter will show, however, these instruments were theory-laden; they revealed novel details but also interposed a screen between observer and object. When academicians examined a plant with the microscope or the air pump, they saw not just a plant but also a link in an evidential chain that was not primarily botanical. Indeed, the cogency of their research depended on the theoretical certainty of the discipline that stimulated them to use the new apparatus. Thus, microscopic and pneumatic botany had different fates: the Academy used microscopes to support theories about physiology, but it used the air pump to clarify theories about air and the void.
The New Instruments and Botany
New theories, experiments, and observations were the hallmarks of seventeenth-century science. They often depended on recently invented instruments quickly applied to the most varied research. Scientific apparatus such as Galileo's telescope and Torricelli's tubes helped revolutionize the way people thought about the universe. It also had theoretical implications that remained fertile and controversial for decades.
The bounteous yield of data and hypotheses provoked many debates. Exactly what could be learned from the new instruments was unclear, since both the phenomena observed and the inferences drawn were generally called into question. Hence, the four instruments that transformed scientific research in the seventeenth century — the telescope, barometer, air pump, and microscope — opened an uncertain world to their earliest users. The Baconian ideal of compiling an encyclopedia of discrete facts about the world could not suffice when such instruments demonstrated the controvertibility of data and forced savants to adjudicate between discovery and theory.
The new instruments were puzzling but irresistible. Savants and amateurs both were enthusiastic about them. By the 1660s, many people wanted to perform the latest experiments on the most modern equipment or to see demonstrations of controversial phenomena with their own eyes. Private scientific societies whose sponsors could not afford up-to-date apparatus found their inquiries fettered, and dedicated experimentalists became exasperated by dilettantish amateurs who preferred discourse to
experiment. Many savants worked with artisans to design and construct novel devices or to improve the quality of essential ingredients such as glass. Curiosity and optimism about the new tools permeated scientific inquiry, and any self-respecting savant required a sometimes expensive range of equipment.
The scientific institutions organized in the latter half of the century reflect this enthusiasm. As curator of machines and experiments at the Royal Society, Robert Hooke demonstrated the latest experiments and equipment at meetings. Members of the Accademia del Cimento had at their disposal the laboratories and instruments of the Medici princes and became known throughout Europe for their experiments, especially with the Torricellian void, which were widely imitated. The Academy of Sciences collected models of new machinery and bought instruments for astronomical observations, surveying, dissections, and other research. In the best seventeenth-century tradition, academicians were inventors as well as users of apparatus. Several developed surveying instruments for use at Versailles. Auzout devised a micrometer, and Roberval described a new balance, while Huygens designed clocks, microscopes, and air pumps and briefly thought he had discovered a new kind of barometer.
The Academy employed instruments in its botanical studies to analyze plants chemically, to anatomize plants, and to clarify vegetable physiology. Of these activities, chemical analysis was least affected, because the only new instruments used were the aerometer (a device for determining the specific gravities of plant extracts) and the thermometer. In their chemical analysis, academicians sought the constituents of organic matter and looked for patterns in their data. They had an idea, not a theory, and while the aerometer provided more information, it did not offer the interpretive key.
More provocative were the Academy's studies of plant anatomy and physiology with the microscope and air pump. Here academicians could relate their findings to a broader range of theories and analogies, because both instruments had already been deployed in other fields. The microscope and the air pump opened plant studies to several interdisciplinary influences: microscopy connected vegetable and animal anatomy, and the air pump linked plant growth to the properties and effects of air. The botanical applications of these instruments at the Academy draw attention to some lesser known aspects of seventeenth-century botany and clarify the impact of new inventions on scientific theorizing.
Early Botanical Microscopy at the Academy
Microscopes had already been used to study plants by the time the Academy was founded, but only a few academicians were interested in botanical microscopy. As a result, microscopic observation affected the Academy's natural history of plants only peripherally. Descriptions were meant to distinguish plants from one another, but not to include their anatomies or to clarify vegetable physiology. The engravers found microscopes useful, because the Academy wanted the smallest external details of each part of the plant to appear. Otherwise, academicians only occasionally used microscopes to study plants.
Perrault recommended microscopy for research on germination. In 1667 he made these plans:
Experiments on how plants grow will be made by considering the roots and seeds and examining them diligently with the microscope, both before placing them in the ground, and by taking them out of the ground at various times in order to consider the different changes which occur with respect to size, or to shape of their pores, to their saps, weight, color, odor, taste, and so on. Then one will consider what happens to their sprouts when they begin to grow, especially to those which are enclosed within large seeds, such as acorns, where one notices the root, the trunk, and the branches of the entire tree, which seems already formed and distinct before emerging between the two sections into which the acorn normally separates.
Perrault hoped that microscopes would settle disputes over preformation and emboîtement and would ease comparisons between the growth of seeds and the development of the chick in an egg.
Although Perrault's suggestions were not officially adopted, some members studied plants with microscopes and magnifying glasses. Examining hemp thread (fil de chanvre ), La Hire saw filaments which he compared to capillary tubes and claimed that sap passed up them to nourish the plant. Dodart examined young shoots of wheat to find the tiny grains; he was testing preformationist theory. In the 1680s some academicians considered studying plants and their distillants with the microscope. Not institutional policy but individual interests incorporated microscopes into the arsenal of discovery and argument in botany.
Unlike most of his colleagues during the 1660s and 1670s, Mariotte routinely used hand lenses and compound microscopes. They were invaluable in his studies of vegetable physiology. His arguments against preformation and for the circulation of the sap depended on meticulous observations.
He examined leaves, bulbs, seeds, and cut stems; his descriptions of bark, skin, fibers, vessels, spongy matter, and saps are the verbal equivalent of Grew's illustrations. In shrubs he identified "canals or pores" in the marrow of the cutting; a microscope revealed these pores to be "several small oval cells [cellules ]" resembling honeycombs.
Without a lens Tournefort could not have found the "seeds" of ferns or examined the growth, desiccation, and contraction of seed cases, observations that he cited against spontaneous generation. When he examined plant vessels Tournefort found resemblances to bones and muscles, and he claimed that the very vessels that carried sap eventually dried and became fibrous, stiff, woody, and capable of supporting the plant. Microscopy provided evidence for Tournefort's theories about the motion of sap and the growth and reproduction of plants.
Huygens contributed incidentally to botanical microscopy when he brought a spherical microscope to the Academy in the summer of 1678. Although his primary interest was animalcules, his colleagues examined a section of a fir tree, some pollen from a lily, and the marrow of a fig tree. But Huygens's apparatus held little interest for the botanists, and besides him only the astronomers Picard and La Hire used it to study plants, or rather their pollen. Picard compared the shapes of pollens from different plants, without conjecturing about the nature or function of that "dust" or "flour." He merely commented on the shapes, colors, and structures of pollen. Huygens and his brother Constantyn went beyond Picard's simple comparisons of appearance. They considered internal structure and the connection between pollen and the activities of bees. Huygens observed that the "dust" of crocus flowers and the dust on bees' feet looked the same, and he argued that pollen adhered to the feet of bees, who made wax from it. When his brother expressed surprise that pollen stored for two months still contained a liquid, Huygens replied, "What you say of the liquid in yellow powder confirms again what I said, that it served to make wax." Although he hypothesized about accidental uses of pollen, Huygens never applied his observations of pollen to any theories about plant physiology. No one in the Academy took more than passing notice of his or Picard's findings.
Only one of the academicians who normally studied botany, La Hire, used Huygens's spherical microscope to examine plants. This surprising lack of interest among the Academy's botanists was due to the difficulty of using the spherical microscope and to its limited range of applications. Huygens noted that many of his colleagues saw animalcules only with great effort, while others never saw them at all. Proper use of the lens and
careful mounting of the object were crucial for success. Huygens, Roemer, and Hartsoeker developed a way of mounting several objects on a rotating wheel, an invention to which no Frenchman contributed, Huygens was quick to point out. But even when every precaution was taken, the instrument was of limited use for studying plants, because it was not yet possible to cut plant sections so thin as to be transparent or to fit between slides. Few parts of plants, therefore, lent themselves to study with Huygens's apparatus.
Despite their inherent defects and the difficulty of using them, spherical microscopes impressed Parisian scientific savants. Huygens was as gratified by the reception of his microscopes as by the inability of Parisians to make the lenses. He reported that "the curious" were "astonished by the great effect it makes"; Locke had heard of "the extraordinary goodness" of Huygens's microscope. Protestations of interest no doubt outnumbered clear sightings of animalcules, because the skepticism that had earlier greeted the telescope and air pump was now less tenable; by 1678 few amateurs would have chanced embarrassment by challenging Huygens on the basis of negative evidence. Instead, Huygens's enemies contented themselves with ghost-written articles disproving Huygens's claims of priority.
Microscopy was always ancillary to other ways of studying plants at the Academy. Academicians who habitually studied the natural philosophy of plants used a convex hand lens and sometimes a compound microscope to observe the details of plant anatomy and to support various hypotheses about plant physiology; they applied the readily available microscopes to subjects that had long interested them. Huygens and Picard, on the other hand, were more engrossed by the novelty of the instrument than by its botanical applications; they never pursued plant microscopy exhaustively because they were more interested in other subjects. Finally, academicians who studied the anatomy and physiology of plants preferred theoretical issues to exhaustive description. For them microscopy was one technique among many, and they used it along with naked-eye observation, chemical analysis, and analogical reasoning in order to support their hypotheses about germination, nutrition, and growth.
Plants and the Air Pump
The air pump was one of the most controversial inventions of the seventeenth century, because the evidence produced with it was cited by both sides in the debate over the existence of a vacuum. To determine whether a void could exist, natural philosophers placed small animals,
their own arms, lighted candles, bells, and magnets into glass receivers, from which they evacuated air. After observing the asphyxiation of mice and birds, the rise of blood to the surface of an arm, the extinction of a flame, and so on, savants acknowledged that an evacuated receiver held little or no air. But they could not agree on whether or not another substance took the place of air, thereby preventing the formation of a vacuum.
It was natural that plants also be tested. Air pumps excited the experimental impulse in their early users, who compared the behavior of as many different objects as possible in their machines. But experiments on plants were not popular, for the results were never spectacular. Juice running out of a pricked fruit was less impressive than nearly suffocating a canary only to revive it by readmitting air to the evacuated chamber. Waiting several days to ascertain whether a plant would die in an evacuated bell jar was tedious by comparison with testing whether a ringing bell sounded in an airless environment. Where plants were simply part of a comparative analysis of the effects of airlessness, they were among the less interesting subjects of study.
Some savants, however, thought the air pump could shed light on botany. Sir Kenelm Digby, for one, had already suggested that air might be important to plants, and in the 1660s and 1670s Hooke tested seeds with an air pump for the Royal Society, after a request from Boyle. In the Academy, Borelly once suggested testing plant distillants and earth in an evacuated receiver, and Huygens and Homberg examined the growth of plants in a vacuum. Academicians narrowed the question: instead of asking whether air was somehow important to plants, they inquired more specifically whether the presence of air was a necessary condition for the germination of seeds.
Huygens was a pioneer in the development of the air pump and was the first academician to use it. He recommended experiments with it in a 1666 memorandum to Colbert and brought his own machine to the Bibliothèque du roi when he moved in that year. In the spring of 1668 he introduced the air pump to his colleagues, starting with simple demonstrations calculated to interest his audience and drawn from his private research of 1662. He pricked the skin of an apple and placed the apple in the receiver: juice ran out of the fruit as air was removed from the jar. He made spirit of wine bubble by evacuating a receiver. Having demonstrated what the machine could do, Huygens designed an experiment that he characterized as "more important," because it would ascertain whether seeds and plants could grow in a vacuum.
With this experiment, Huygens introduced the Academy to the use of the air pump in botanical research. All subsequent tests followed the same pattern: plants, seeds, branches, and soil were placed in the receiver, or bell jar, which was evacuated and removed from the pump; its contents were observed over a period of several days. Huygens evacuated the bell jar until his measuring device indicated there was no more air inside. Then he removed the bell jar from the pump and observed it for about eight days.
One of the risks to botanists was that even when the initial pretext of these experiments was botanical, their ultimate interest often lay in unexpected side-effects that were inconsistent with the known properties of air. Huygens's test set the pattern in this respect as well, for he was surprised to discover a puddle of water on the floor of the bell jar, and this deflected his attention from the plants. Huygens explained the puddle by saying that the soil had exhaled some vapors that condensed on and ran down the walls of the bell jar, but he was puzzled that vapors could rise in a vacuum when feathers fell like lead. As the experiment continued, Huygens observed additional phenomena that seemed to confirm that vapors rose, and he concluded that the vapors were being converted into air. As for the plants and seeds, while they did not grow or flower more, neither did they die as expected in an airless atmosphere.
Huygens later tried to re-examine how lack of air affected plants, using not an evacuated receiver but a double bottle. In May 1672 he sealed the bottle, which was one-quarter full of earth; when he brought it to a meeting in August 1675, more than three years later, academicians observed that a large amount of grass and some moss had grown in it, even though air had not entered the bottle. Both of Huygens's experiments puzzled academicians, for they seemed to show that air was not necessary for the growth of plants.
The Academy dismissed such issues from its collective mind until Homberg revived them two decades later. Like Huygens, Homberg perceived experiments on germination in a vacuum primarily as tests of the nature and functions of air. He performed only two such experiments with plants. The first was brief and improved on Huygens's test of 1668 by including a control, while the second was more elaborate and more carefully considered for its implications about germination.
In the first, Homberg sowed seeds in two boxes, placing one under a glass dome and the other in a receiver, which he evacuated and then placed beside the glass dome in a window with a southern exposure. On the first evening, he noticed that the earth in the vacuum had split in several places and that drops of water covered the sides of the receiver; on the base of the
receiver was more water, which seemed to be the liquid used to moisten the soil at the start of the experiment. In the control box the soil was not so cracked and the glass dome was covered with less water; some water had fallen onto the stone base, but because the base had cracked and water had escaped, Homberg could not measure it. He attributed the excess liquid in both containers to evaporation and condensation, and he thought there had been less evaporation under the glass dome than in the evacuated receiver. He did not try to explain why the earth cracked, nor did he continue the experiment long enough to see whether seeds germinated in one container or the other. Homberg explained evaporation and condensation in a vacuum, which had troubled Huygens in 1668, as the effect of "ethereal matter," which forced vapor against the sides of the receiver, where it became water and ran to the bottom.
Homberg's second experiment lasted about six weeks, from 1 May through 12 June 1693, and like the first had been designed with a control. He sowed the seeds of five plants — purslane, cress, lettuce, chervil, and parsley — in two small boxes. One box he placed in a receiver, the other he left in the open air. He evacuated the receiver every morning and watered each box every third day.
Homberg recorded the weather and the daily appearance of the shoots, noting withering and death, the sizes of the shoots, and any continued growth. In the evacuated receiver, chervil and parsley never germinated, and purslane, cress, and lettuce began to grow much later than did their counterparts in the open air; purslane died the day after its shoot appeared in both boxes; cress in the receiver died five days after it first appeared; lettuce grew very tall in the receiver, but its leaves were small and, after an initial rapid growth, it stopped growing entirely.
Homberg decided to test whether seeds that had not germinated in the vacuum would do so when exposed to air. On 25 May he admitted air to the receiver and then closed the stopcock to prohibit air from passing into or out of the vessel. Chervil, purslane, cress, and parsley germinated, but shoots that had developed in the vacuum did not change. On 7 June Homberg removed the box from the receiver, but by 12 June all had died.
Because some seeds had germinated in the evacuated receiver, Homberg decided that neither the weight nor the elasticity of air could be the principal cause of germination. But fewer seeds germinated in the receiver than in the open air, and none of the seedlings in the evacuated bell jar grew normally or survived more than a few days. Homberg therefore concluded that air was "at least an accidental cause" of germination.
Trying to explain how a vacuum could injure seeds, he argued that the
seeds contained air which "dilates because of its spring rather more easily in the void, where nothing impedes it, than in the air where it is pressed on all sides." Seeds exposed to a vacuum were, therefore, damaged by the expansion of the air they contained, and "since the organs that serve to carry and to distribute nourishment are ruptured, germination cannot take place." A damaged seedling could grow but would not develop into a healthy plant.
Homberg noted three additional phenomena in the evacuated receiver: the soil swelled, a fungus grew, and drops of water formed at the tops of the seedlings. He believed the soil changed because of moisture and air. Moisture penetrated and broke down small masses of earth; it filled the small spaces between clumps of soil, making the earth seem oily, soft, and slimy. Assuming that air was "mixed with the new water" used to moisten the soil, and that air expands in a vacuum, Homberg argued that its "effort" to escape accounted for the "swelling and bubbling" he had noticed in the soil.
The second striking phenomenon was the appearance of what was probably the fungus pythium on the surface of the soil. Homberg first noticed this on the eighth day of the experiment, when he thought that "the earth enclosed in the vacuum had changed color" and seemed from certain angles to be "grayish and shining." Examining the surface of the soil with a microscope, he observed "a lot of small transparent and grayish filaments that looked like a spider's web":
Some of these filaments were straight, others rested on the soil and were attached to small protrusions of earth; since they were crisscrossed, they formed a sort of fabric so strong and tight that the water with which we wetted the soil was held there and formed drops as big as beans, without moistening the soil.
He tasted them, expecting a flavor of saltpeter because they resembled the mildew on the walls of cellars. But he noticed no taste at all and did not test the substance with any of the chemical reagents commonly used in the Academy's laboratory.
Finally, Homberg observed guttation induced by the vacuum: at the top of each seedling in the void there was always a drop of water; when it ran down the stem, a new drop formed immediately. Homberg claimed that "this water did not come out of the pores of these sprouts," but attributed it instead to vapors formed in the void by the action of ethereal matter on damp earth. He believed these droplets were the equivalent of the drops of water he had observed on the glass walls of the receiver in his previous experiment. Homberg was perplexed and wondered, just as Huygens had
twenty-five years earlier, how drops of water could rise in a vacuum, when light objects fell.
Homberg believed that an airy matter was present in substances such as water and seeds. This led him to expect air to reappear in an evacuated, well-sealed bell jar, if it held any substances containing airy matter. But he did not classify plants as air-producers, and neither he nor Huygens thought that plants could produce the drops of water observed on leaves. Analogies with dew or with the condensation of water on a glass dome were so persuasive that Huygens and Homberg did not suspect that plants might exude water, even though contemporaries like Mariotte had shown that leaves could absorb moisture, and John Wallis had demonstrated transpiration experimentally. But Homberg never drew on such notions to explain the phenomena he observed with the air pump, seeing his studies as useful to botany but not vice versa.
Some of the peculiarities of pneumatic research on plants were due to its having been borrowed: the air pump was initially developed in other countries, and those who performed experiments with it were trained in and inspired by other disciplines. The air pump never caught on as an experimental tool at the Academy, despite Huygens's enthusiasm, and such experiments as Huygens performed in Paris were often modeled on those of his English colleagues. Thus, Boyle influenced Huygens as much in his choice of experiments as in his development of the pump itself. Huygens was also familiar with Digby's discourses on vegetation, which, with their arguments that plants depend on a vital nutritious substance in the air, may well have stimulated Huygens's tests of 1668 and 1672.
Claude Perrault was unusual in connecting Huygens's studies of the vacuum to his own explanations of how sap rises. He also used pneumatic observations to refute Duclos's claim that an "expulsive faculty" in branches and trunks propelled sap into the roots. Perrault pointed out that "plants that are filled with a lot of sap" simply "let it flow," but when the receiver is evacuated, so that "the compression of the air is reduced, the sap dilates and becomes less condensed than it had been." He believed that this experiment, which was not one of those demonstrated by Huygens in 1668, showed that the weight of the air — and not any expulsive faculty — pushed juices from or through plants, thus causing sap to move.
Curiously, while animal physiology often influenced plant physiology, it had relatively little effect on how academicians interpreted vegetable phenomena in the vacuum, even though academicians also tested animals with air pumps. Perhaps Homberg derived his theory that a vacuum destroyed the internal organs of seeds from observing the damaged muscles and
organs of animals that had died in evacuated bell jars. Otherwise academicians explained the physiology of seeds with references to the passive, absorptive qualities of dead sponges. Thus, seeds were said to absorb water like sponges and to germinate by swelling, until they burst their shells and developed into new shapes; savants wanted to know whether moist seeds would inflate in a vacuum as sponges did. This question, not the example of small animals dying in evacuated receivers, motivated Homberg to study seeds.
Experiments on plants in an evacuated receiver held little interest for academicians, and Huygens's and Homberg's tests mostly went unnoticed. Since air pumps were used primarily to test the weight and elasticity of air, it was always these properties that academicians cited to explain what happened to seeds and plants. In any case, vegetable behavior seemed less interesting than the other phenomena associated with botanical pneumatics. Putting plants in the air pump represents not a successful interdisciplinary exchange but isolated studies whose anomalies sidetracked academicians from answering questions about plants.
Scientific instruments did not play a major role in botanical research at the Academy. They were used only infrequently to examine plants, and very often the issues addressed were not botanical. Plants in a vacuum tested theories about the properties of air and the effects of airlessness. Instead of using microscopy to explore plant anatomy systematically, academicians sought only such observations as would address specific physiological theories.
Academicians had no program, and their research was piecemeal and lacked continuity. Patronage was irrelevant, because the microscopes, thermometers, and aerometers were inexpensive enough that academicians could have bought them with their own funds, while the air pumps were designed and owned by the academicians themselves. In these respects the Academy was no better than the private societies. Yet it was less Baconian than its rivals and its institutional continuity counteracted the centripetal individualism of physiological research.
The two principal instruments used to study plants, the microscope and the air pump, were of different value to botanists. The microscope had a more established place, because it seemed to provide clearer and more definitive evidence. Mariotte, La Hire, Tournefort, and their contemporaries knew how to describe what they saw. They could relate their observations
to zoological models and could fit them into accepted patterns of thought about plants. Plant microscopists evoked two paradigms, one factual and the other logical, and such appeals to zoology and to analogical reasoning enabled botanists to explain what they saw through the lens.
With the air pump, however, savants were unsure of themselves. Experiments with plants were designed to ascertain whether plants were like animals in requiring air for their vital functions, but plants behaved inconsistently in the vacuum: some seeds sprouted while others did not, some seedlings died immediately while others survived and grew for a day or two. Unexpected and confusing phenomena — the excessive production of water, the appearance of gray filaments, the cracking and expansion of the soil — occurred in every experiment. Botanical pneumatics fell prey to disputes between conflicting theories about air and the vacuum. Academicians were cautious, therefore, in interpreting their observations of plants in the vacuum and did not build on this research.
Scientific apparatus offers decisive evidence only within the context of a paradigm that allows savants to identify and understand crucial phenomena. But in the late seventeenth century, botany was changing, and its new accretions depended on borrowed theories that sometimes failed. When academicians used new tools to study plants, their research seemed meaningful if the cross-disciplinary analogies worked, but otherwise they could not interpret their findings. Without a satisfactory theory, studies of plants simply accumulated evidence on both sides of debates about other natural phenomena, as the case of botany and the new instruments reveals.