2 
BACTERIOLOGY. 
Experi¬ 
ments 
proving 
Spontane¬ 
ous gen¬ 
eration 
incorrect 
their source and mode of origin. Among the lowest 
forms of aninjal life known at that time were the 
maggots found in putrefying meat. It was supposed 
that they developed from; the meat during the pro¬ 
cess of putrefaction. The animalcules of von Leeu- 
wenhoeck too were believed to originate spontane¬ 
ously. This theory of spontaneous generation held 
sway and, although there were many opposed to this 
doctrine, it was not until nearly a hundred years later 
that Spallanzani ( 1769 ), an Italian, tried by experi¬ 
ment to show that micro-organisms could not develop 
in this way. He took animal matter and mixed it with 
water in a flask. After boiling the mixture and seal¬ 
ing the neck of the flask he found that it could be 
kept for a long time without putrefying and without 
any micro-organisms developing in it. This experi¬ 
ment was subjected to much criticism, however, be¬ 
cause the air so essential for the development of life 
was excluded by sealing the flask. This objection 
was met by modifying the experiment, first by ad¬ 
mitting air that had passed through strong sulphuric 
acid, and later by filtering the air through cotton 
used to plug the mouth of the flask. It remained for 
Pasteur (i 860 ) to settle the question beyond dispute 
by showing that the entrance of dust into mixtures 
that had been boiled was sufficient to set up putre¬ 
faction on account of the germs carried in with it. 
So long as the air was filtered free of germs by cot¬ 
ton plugs, just so long the mixtures remained free 
from growth. 
