DEVELOPMENT OF THE BACTERIA. 1¥3 
Cohn, in order to better observe the phenomena 
and to get rid of the moulds, which the cane-sugar 
caused to develop too rapidly, employed the fol- 
lowing culture-fluid : — 
Distilled water. . . .. FOO: 
Tartrate of ammonia . . ft: 
ASHES: OF Venst “<2 *2 go <4 ie 
Bacteria develop in this fluid wonderfully, which 
proves that sugar is not indispensable to them. 
One other solution often employed is that of 
Mayer. It has the advantage of not requiring the 
employment of ashes of yeast: — 
Phosphate of potash . . . 0.1 gramme. 
Sulphate of magnesia. . . 0.1 ,, 
Tribasic phosphate of lime . 0.1 ,, 
Diseilled water "02S 2064. 
Cohn adds to this 0.2 gr. tartrate of ammonia. 
En resumé, the bacteria can take nitrogen, which 
they need in order to form their protoplasm, either 
from albuminous compounds, which they decom- 
pose, as in putrefaction, or in the form of am- 
monia, or, perhaps, by borrowing it from nitric 
acid, but this last source is not well established 
(Cohn). 
Carbon.—In addition to the sources common 
to other organisms, the bacteria can take this im- 
portant element of their composition, under cer- 
tain circumstances, from the organic acids. Thus, 
when we cultivate bacteria in a solution containing 
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