68 MICROBES, FERMENTS, AND MOULDS. 
caproic acids, under the influence of nitrogenous 
substances and of the air; the change into glucose 
of gums, of starch, of dextrine, of sucrose, and mannite; 
the transformation of these substances into each other 
under the influence of living agents, or of those 
belonging to a living organism; the transformation 
of such glucosides as populin, salicin, tannin, etc., 
into sugar, or into neutral or acid substances ;—all 
these phenomena are fermentations (A. Gautier). 
We may even go further. The germination of 
seeds and the ripening of fruit are accompanied by 
phenomena of the same order. In animals, gastric, 
pancreatic, and. intestinal digestion, together with other 
changes connected with nutrition and assimilation 
which take place in the blood and in all the organs, 
may be considered as true fermentations. In this case 
the cells of our tissues and the blood-corpuscles play 
the part of yeast in effecting alcoholic fermentations. 
Finally, the miasmatic, virulent, and contagious 
diseases, which we shall study in another chapter, 
are also caused by changes in the blood and in the 
other fluids of the system, and should be considered 
as fermentations, produced by minute microscopic 
organisms analogous to ferments, and which are, as 
we shall presently show, bacteria or microbes, strictly 
so-called. The putrefaction of dead bodies is also 
a fermentation. 
We shall, in this place, only consider the fermen- 
tations which are used in manufactures, 
