I have noticed in the Preface to the Second and Third Editions (S. xiii., p. xii. English Trans.) the subject of the republication here of the preceding pages, which were first printed in Schiller's Horen (Jahrg. 1795, St. 5, S. 90-96). They contain the development of a physiological idea clothed in a semi-mythical garb. In the Latin "Aphorisms from the Chemical Physiology of Plants" appended to my "Subterranean Flora," in 1793,—I had defined the "vital force" as "the unknown cause which prevents the elements from following their original affinities." The first of my aphorisms were as follows:—Rerum naturam si totam consideres, magnum atque durabile, quod inter elementa intercedit, discrimen perspicies, quorum altera affinitatum legibus obtemperantia, altera, vinculis solutis, varie juncta apparent. Quod quidem discrimen in elementis ipsis eorumque indole neutiquam positum, quum ex sola distributione singulorum petendum esse videatur. Materiam segnem, brutam, inanimam eam vocamus, cujus stamina secundum leges chymicæ affinitatis mixta sunt. Animata atque organica ea potissimum corpora appellamus, quæ, licet in novas mutari formas perpetuo tendant, vi interna quadam continentur, quominus priscam sibique insitam formam relinquant.
