[Footnote 1:  “Das entraethselte Geheimniss der geistigen Gaehrung (Vorlaeufige briefliche Mittheilung)” is the title of an anonymous contribution, to Woehler and Liebig’s “Annalen der Pharmacie” for 1839, in which a somewhat Rabelaisian imaginary description of the organization of the “yeast animals” and of the manner in which their functions are performed, is given with a circumstantiality worthy of the author of Gulliver’s Travels.  As a specimen of the writer’s humour, his account of what happens when fermentation comes to an end may suffice.  “Sobald naemlich die Thiere keinen Zucker mehr vorfinden, so fressen sie sich gegenseitig selbst auf, was durch eine eigene Manipulation geschicht; alles wird verdaut bis auf die Eier, welche unveraendert durch den Darmkanal hineingehen; man hat zuletzt wieder gaehrungsfaehige Hefe, naemlich den Saamen der Thiere, der uebrig bleibt.”]

However, it may be asked, is there any necessary opposition between the so-called “vital” and the strictly physico-chemical views of fermentation?  It is quite possible that the living Torula may excite fermentation in sugar, because it constantly produces, as an essential part of its vital manifestations, some substance which acts upon the sugar, just as the synaptase acts upon the amygdalin.  Or it may be, that, without the formation of any such special substance, the physical condition of the living tissue of the yeast plant is sufficient to effect that small disturbance of the equilibrium of the particles of the sugar, which Lavoisier thought sufficient to effect its decomposition.

Platinum in a very fine state of division—­known as platinum black, or noir de platine—­has the very singular property of causing alcohol to change into acetic acid with great rapidity.  The vinegar plant, which is closely allied to the yeast plant, has a similar effect upon dilute alcohol, causing it to absorb the oxygen of the air, and become converted into vinegar; and Liebig’s eminent opponent, Pasteur, who has done so much for the theory and the practice of vinegar-making, himself suggests that in this case—­

“La cause du phenomene physique qui accompagne la vie de la plante reside dans un etat physique propre, analogue a celui du noir de platine.  Mais il est essentiel de remarquer que cet etat physique de la plante est etroitement lie avec la vie de cette plante."[1]

[Footnote 1:  “Etudes sur les Mycodermes,” Comptes-Rendus, liv., 1862.]

Now, if the vinegar plant gives rise to the oxidation of alcohol, on account of its merely physical constitution, it is at any rate possible that the physical constitution of the yeast plant may exert a decomposing influence on sugar.