254 PARASITIC BACTERIA. 
the body and is dependent upon their normal functions. It is only 
the living cell which can resist the invasion of microorganisms, 
either wholly or partially. From this it follows that the resistance 
will be greatest when the body cells are in the highest state of 
physical activity, and will diminish when they become somewhat 
impaired in vitality. Anything which tends to reduce the physical 
health of the individual tends to reduce his power of resistance. 
For example: sometimes an individual shows a great tendency 
to develop boils or abscesses, and but little power of resisting them. 
We say his "blood is in a bad condition." By this is really meant 
that his body activities are so repressed that he is unable to resist 
the invasion of some of the common bacteria which are present on 
every hand and which an individual in healthy condition easily 
repels. If his physical vigor can be restored, the troubles will 
disappear, although the bacteria which produce the boils and 
abscesses are just as abundant around him as before. Physical 
vigor is the best protection against the invasion of parasitic bacteria, 
and a weakened physical condition invites attack. 
This matter is emphasized here because it is too generally lost 
sight of in the combat against infectious diseases. During the first 
years of the study of bacteriology there was a very general tendency, 
in the attempt to avoid diseases, to place the whole emphasis 
upon the methods of avoiding bacteria. If a disease is caused by a 
bacterium, what more natural method could be suggested for 
avoiding it than to avoid the bacterium? In accordance with this 
idea there developed a long series of rules and regulations suggested 
by bacteriologists and adopted by health boards, all designed for 
the prevention of the distribution of disease germs. This is, 
indeed, the foundation of modern sanitation. 
Increasing of Individual Resistance. Recently there has 
been a manifest reaction against this one-sided attitude. While 
the importance of preventing the distribution of bacteria is still 
acknowledged, there is to-day a growing recognition of another 
side to the question. The strengthening of personal vigor is of no 
less importance many believe it is of more importance than 
the preventing of the distribution of bacteria. The weakening of 
