DEVELOPMENT OF THE BACTERIA. 103 
Finally, Bastian, having succeeded in obtaining 
bacteria in liquids which he believes deprived of 
every germ, believes in their spontaneous genera- 
tion. The following is a résumé of his experiment : 
Normal acid urine is brought to the boiling- 
point, then a solution of potash (in sufficient quan- 
tity to neutralize the volume of urine employed) 
is also brought to the boiling-point; after cooling, 
the two liquids are mixed, and the whole placed 
in an oven at 50°. At the end of two or three 
days, bacteria are developed. 
Pasteur points out three causes of error in the 
experiment of Bastian: 1. The germs may come 
from the urine; 2. The germs may come from the 
solution of potash; 3. The germs may be fur- 
nished by the vessels employed in the experiment. 
In support of this criticism, Pasteur has made some 
similar experiments, guarding against these causes 
of error, and has not obtained bacteria. 
DISSEMINATION OF BACTERIA IN AIR AND WATER. 
Air. — The experiment of Pasteur for gathering 
atmospheric germs is well known. He fixes a 
glass tube in an aperture made in a window-blind. 
The extremity of the tube, which communicates 
with the open air, is closed with a plug of cotton, 
to the other extremity is attached an aspirator. 
When the air has filtered through the cotton for 
some hours, this is examined, and is found to be 
filled with germs. 
