21 
which surround them, eens the very small portion which 
they can use, and leavin e form 
tie] 
i" 
o 
% 
Be 
a 
s 
au 
° 
ta 
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7 
It is of prime importance to know the methods by which the 
different germs are ordinarily introduced into the system. Some, 
as those of typhoid and cholera, are practically incapable of in- 
is manifestly the avoidance of infection and contagio rfec 
accomplishment of this result is well-nigh impossible, but since 
e me of an attack depends largely e nu ro 
a 
germs making it, careful protection is at all times to be recom- 
mende 
ieee protection involves special methods in the case of 
each germ, as their habits and offensive and defensive powers 
Sitter among themselves. Some require oxygen, others are de- 
