general bacteriology 
31 
This varies, as regards the individual constituents, to 
some extent; for example, the tubercle bacillus contains 
less proteins (8 per cent) but much more fats (3.5 to 4 
per cent). 
The proteins contained in its bacteria are the nucleopro- 
teins, globulins and special proteins. The bacterial ashes 
are mostly chlorides and phosphates of sodium, potassium, 
magnesium and calcium. 
Like other vegetable and animal cells, the bacterial 
cell reacts to the pressure which exists between its own 
protoplasm and the surrounding medium—the so-called 
osmotic pressure, which governs the exchange of the sub¬ 
stances within and without the bacterial cell, this depend¬ 
ing upon the permeability of the cell membrane (the 
ectoplasm), which permits certain substances to enter or 
leave the bacterial cell. 
VI. Nutrition of Bacteria 
In order that the bacteria may live and multiply they 
must have the following substances: 
Carbon. —This they may obtain from proteins, fats or 
carbohydrates. 
Oxygen. —This is obtained by the majority of bacteria 
directly from the atmosphere in the form of free oxygen. 
Not all bacteria, however, need oxygen, and some, as will 
be mentioned later, can not live in its presence. 
Nitrogen. —This is taken in most cases, from proteins. 
There is quite an individual predilection for the special 
proteins required by different bacteria: the gonococcus, 
for example, grows best on uncoagulated human blood 
serum; the influenza bacillus requires hemoglobin (the 
coloring matter of the red blood cells) ; while the diph¬ 
theria bacillus grows best on the coagulated beef serum. 
