"Vim internam, quæ chymicæ affinitatis vincula resolvit, atque obstat, quominus elementa corporum libere conjungantur, vitalem vocamus. Itaque nullum certius mortis criterium putredine datur, qua primæ partes vel stamina rerum, antiquis juribus revocatis, affinitatum legibus parent. Corporum inanimorum nulla putredo esse potest." (Vide Aphorismi ex doctrina Physiologiæ chemicæ Plantarum, in Humboldt, Flora Fribergensis subterranea, 1793, p. 133-136).
I have placed in the mouth of Epicharmus the above propositions, which were disapproved by the acute Vicq d'Azyr, in his Traité d'Anatomie et de Physiologie, T. i. p. 5, but are now entertained by many distinguished persons among my friends. Reflection and continued study in the domains of physiology and chemistry have deeply shaken my earlier belief in a peculiar so-called vital force. In 1797, at the close of my work entitled "Versuche über die gereizte Muskel und Nervenfaser, nebst Vermuthungen über den chemischen Process des Lebens in der Thier und Pflanzenwelt" (Bd. ii. S. 430-436), I already declared that I by no means regarded the existence of such peculiar vital forces as demonstrated. Since that time I have no longer called peculiar forces what may possibly only be the operation of the concurrent action of the several long-known substances and their material forces. We may, however deduce from the chemical relations of the elements a safer definition of animate and inanimate substances, than the criteria which are taken from voluntary motion, from the circulation of fluids within solids, from internal appropria-
