386 THE CAUSES OF THE : XI 
to you—and then finding those extraordinary 
anomalies, as in the case of the mercury bath and 
the milk, he set himself to work to discover their 
nature. In the case of milk he found it to be a 
question of temperature. Milk im a fresh state is 
slightly alkaline ; and it is a very curious cireum- 
stance, but this very slight degree of alkalinity 
seems to have the effect of preserving the organ- 
isms which fall into it from the air from being 
destroyed at a temperature of 212°, which is the 
boiling point. But if you raise the temperature 
10° when you boil it, the milk behaves like every- 
thing else ; and if the air with which it comes in 
contact, after being boiled at this temperature, is 
passed through a red-hot tube, you will not get a 
trace of organisms. 
He then turned his attention to the mercury 
bath, and found on examination that the surface of 
the mercury was almost always covered with a 
very fine dust. He found that even the mercury 
itself was positively full of organic matters; that 
from being constantly exposed to the air, it had 
collected an immense number of these infusorial — 
organisms from the air. Well, under these cireum-_ 
stances he felt that the case was quite clear, and — 
that the mercury was not what it had appeared to 
M. Schwann to be,—a bar to the admission of these 
organisms ; but that,in reality, it acted as a reservoir 
esi wink the infusion was immediately supplied — 
with the large quantity that had so puzzled him, 
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