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.^[46] 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.^[47] Although Mariotte later agreed that chemical analysis might prove that corpuscles existed, this view never caught on in the Academy.^[48] 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,^[49] while Dodart wanted to uncover "what plants are" and thought that chemical analysis might reveal the intimate structure in plants that produces their effects.^[50]

The main purpose of analyzing plants chemically was to discover their constituents.^[51] But by the mid-1670s, frustrated by distillation, some

academicians became disillusioned about the prospects of understanding the nature of plants.^[52] 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.^[53] 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.^[54] 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.^[55]

The third major goal — understanding nutrition — was Dodart's particular interest.^[56] 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.^[57] 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.^[58] Furthermore, Dodart hoped that chemical analysis would clarify the food chain linking soil, plants, animals, and humans.^[59] 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.^[60]

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.^[61] 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.^[62] Furthermore, by concentrating on simpler problems first, academicians might establish a basis for examining the more complex issues.^[63]

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.