114 PHYSIOLOGY OF THE BACTERIA. 
only tartrate of ammonia with a small quantity of 
mineral salts (phosphoric acid, potash, sulphuric 
acid, lime, and magnesia), they develop rapidly, 
taking their carbon from the tartaric acid. 
Cohn has endeavored to ascertain if other or- 
ganic acids could be assimilated by the bacteria. 
By making use of succinate of ammonia, or neutral 
acetate of ammonia, he has been able to cultivate 
these microphytes. Besides, as Pasteur had already 
experimented with solutions containing lactates, and 
in which bacteria had developed until the salt had 
completely disappeared, we may admit that the 
bacteria can assimilate the organic acids, — tartaric, 
succinic, acetic, and lactic; but tartaric acid seems 
to furnish the best alimentary solution. 
Other substances containing carbon are also as- 
similated by the bacteria,—cane-sugar, milk-sugar, 
glycerine, and even cellulose (according to Mit- 
scherlich). 
Cohn concludes, “ that the bacteria multiply quite 
normally, and in great quantity, whenever they 
find the elements in solution which constitute 
ashes, and that they can take the carbon which 
they need from any organic substance containing 
it, and their nitrogen from ammonia, urea, and 
probably from nitric acid. The bacteria, then, re- 
semble green plants, in that they assimilate nitro- 
gen contained in their cells by taking it from 
ammonia compounds, which animals cannot do. 
They differ from green plants in that they cannot 
draw their carbon from carbonic acid, and only 
assimilate organic substances containing carbon, 
