132 
HOUSEHOLD BACTERIOLOGY 
We are likely to think that because bacteria are so 
small and lowly they cannot do much. But in fact 
they do a great deal. Their life processes are ex¬ 
tremely complex. They are chemical engines of great 
potency. Out of the food which they assimilate they 
manufacture a host of subtle poisons, some of which 
are stored up in their tiny bodies, some set free into 
the fluids of their hosts. This, in fact, is* the front of 
their offending: the poisons which they elaborate and 
set free damage the cells. 
Sometimes these poisons interfere with the neces¬ 
sary performances of the cells close about them, or they 
harm them, but not irretrievably; or they may kill 
them forthwith. Again, they are carried far and wide 
throughout the body, and the heart is enfeebled, the 
brain palsied, or fever dominates the scene. 
This is the situation, then, when disease-producing 
bacteria get in among the living body cells and begin 
to grow, setting free their powerful poisons. It is 
cell against cell—the well-bred, highly differentiated 
cell of the body against the crude, prolific spark of 
matter way down upon her borderland of life, potent 
only to eat, to multiply, to shed abroad its poison. But 
the weapons of both the combatants are poisonous. 
For we should not permit our sympathetic viewpoint 
to obscure the fact that the fluids and the digestive 
juices which our own cells elaborate are poisons for 
bacteria, quite as much as is their stuff for us. It is 
the old story of the survival of the fittest here in this 
