Vice-President’s Address. ie 
constitution of the air which still remained that it was not 
possible for these minute organisms to develop or flourish 
in it. This objection was met in 1836 by F. Schulze, who 
put the question to himself, “Whether the access of atmo- 
sphere, light, and heat to substances in flasks included of 
itself all the conditions necessary for the primary formation 
of animal or vegetable organisms?” To prove that this was 
not the case, Spallanzani’s conditions of absolute freedom 
from germs capable of development in the infusion must be 
obtained ; and, secondly, air perfectly free from germs must 
be admitted to this infusion in considerable quantities. 
Schulze proceeded as follows:—He filled a flask half full 
of distilled water, to which he added various animal and 
vegetable substances. He gives the following description of 
the further methods of procedure :—“I then closed it with 
a good cork, through which I passed two glass tubes bent at 
right angles, the whole being air-tight; it was next placed 
in a sand-bath and heated until the water boiled, and thus 
all parts had reached the temperature of 212° F. While the 
watery vapour was escaping by the glass tubes, I fastened, at 
each end, an apparatus which chemists employ for collecting 
carbonic acid gas; that on the left was filled with con- 
centrated sulphuric acid, and the other with a solution of 
potash. By means of the boiling heat employed, every living 
organism and all germs in the flask or in the tubes were 
destroyed, and all access was cut off by the sulphuric acid 
on the one side and by the potash on the other. I placed 
this easily-removed apparatus before my window, where it 
was exposed to the action of light, and also—as I performed 
my experiments during the summer—to that of heat. At 
the same time I placed near it an open vessel, with the same 
substances that had been introduced into the flask, having 
also subjected them to the boiling temperature. In order 
now to renew constantly the air within the flask, I sucked 
with my mouth several times a day the open end of the 
apparatus filled with a solution of potash, by which process 
the air entered my mouth from the flask through the caustic 
liquid, and the atmosphere entered the flask from without 
through the sulphuric acid. The air was, of course, not at 
