1901). MICROSCOPICAL JOURNAL "7 
hoek were living organisms—vegetable forms—capable of 
growth. 
While yeast was looked upon as an inert substance in 
the act of fermenting, it was impossible to understand 
how it could impart fermentation to other substances ; but 
when it was learned by Latour that the essential element 
of yeast was a growing plant, the phenomenon became a 
perfectly natural consequence of life. 
Not only the alcoholic, but also the acetic, lactic and 
butyric fermentations have been shown to result from the 
energy of low forms of vegetable life, chiefly bacterial in 
nature. Prejudice, however, prevented many chemists 
from accepting this view of the subject and Liebig strenu- 
ously adhered to his theory that fermentation was the re- 
sult of internal molecular movement which a body in the 
course of decomposition communicates to other matter in 
which the elements are connected by a very feeble affini- 
ty. Pasteur was the first to declare and prove that fer- 
mentation is an ordinary chemic transformation of cer- 
tain substances, taking place as the result of the action 
of living cells, and that the capacity to produce it resides 
in all animal and vegetable cells, though in varying de- 
gree. In 1862, he published a paper “On the Organized 
Corpuscles existing in the Atmosphere,” in which heshow- — 
ed that many of the floating particles which he had been 
able to collect from the atmosphere of his laboratory were 
organized bodies. If these were planted in sterile infu- 
sions, abundant crops of micro-organisms were obtaina- 
ble. By the use of more refined methods he repeated the 
experiments of others, and showed clearly that ‘‘the 
cause which communicated life to his infusions came from 
the air, but was not evenly distributed through it.” 
Three years later he showed that the organized corpus- 
cles which he had found in the air were the spores or seeds 
of minute plants, and that many of them possessed the 
property of withstanding the temperature of boiling wa- 
