FERMENTS AND ARTIFICIAL FERMENTATIONS. 71 
Chemists were at first unwilling to admit the 
important part played by yeast in fermentations, and 
in order to explain it, they assumed the existence 
of a very obscure physico-chemical 
phenomenon, to which the name 
of catalysis, or action by presence, 
was given. But in 1848 an illus- 
trious French chemist, Dumas, 
clearly explained the physiological aie a 
function of the living ferment, or oo eae 
yeast. 
“Fermentations,” he writes, “are always pheno- 
mena of the same order as those which characterize 
the regular accomplishment of the acts of animal life. 
They take possession of complex, organic substances, 
and unmake them suddenly or by degrees, restoring 
them to the inorganic state. Several successive fer- 
mentations are, indeed, often required to produce the 
total effect. The ferment appears to be an organized 
being ; . . . the part played by the ferment is played 
by all animals, and by all but the green parts of 
plants. All these beings and organs consume organic 
substances, multiply and restore them to the simplest 
forms of inorganic chemistry.” 
Finally, Pasteur’s memorable labours, which he 
began to publish in 1857, confirmed the new theory 
of fermentation, which no one now doubts. Pasteur 
states that every fermentation has its specific ferment ; 
in all fermentations in which the presence of an or- 
