In science, vegetable life, or "plant life", along with animal life, was one of the two Linnaean classification divisions of living matter used in the pre-Darwinian days of chemistry and biology.

Vegetable life and caloric
In 1787, French chemist Antoine Lavoisier stated that the true elements of vegetables are hydrogen, oxygen, and charcoal and that, in relation to the decomposition of vegetable (and animal) substances by the action of fire that "of these elements, hydrogen and oxygen have a strong tendency to unite with caloric, and be converted into gas, whilst charcoal is a fixed element, having by little affinity with caloric." [2]

With the development of the new science of "thermo-dynamics" in the 1850s, those such as William Thomson, began to postulate on how the new mechanical theory of heat and dissipation related to to "vegetable life" or to the "will of animate creatures". [1]

1. (a) Quote: according to “known facts with reference to the mechanics of animal and vegetable bodies” there is “at present in the material world a universal tendency to the dissipation of mechanical energy” and that “any restoration of mechanical energy, without more than an equivalent of dissipation, is impossible in inanimate material processes, and is probably never effected by means of organized matter, either endowed with vegetable life or subject to the will of an animated creature”
(b) Thomson, William (Lord Kelvin), "On a Universal Tendency in Nature to the Dissipation of Mechanical Energy" (
Google Books) (URL), Proceedings of the Royal Society of Edinburgh for April 19, 1852, also Philosophical Magazine, Oct. 1852, also Mathematical and Physical Papers, vol. i, art. 59, pp. 511.
2. Lavoisier, Antoine. (1787). Elements of Chemistry - in a New Systematic Order, Containing all the Modern Discoveries, (ch XII, pg. 123). New York: Dover (reprint).

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