Our skin is covered
with millions of them, as is every article about us. They can
circulate in the lymph and blood and reach every tissue and part of
our organisms by passing through the walls of the capillaries.
Fortunately, they require certain conditions of temperature, moisture,
air, and organic food for existence and for the preservation of their
vital activities.
If the surroundings are too hot, too cold, or too dry, or if they are
not supplied with a proper quantity and quality of food, the bacterium
becomes inactive until the surrounding circumstances change; or it may
die absolutely. The spores, which finally become full-fledged
bacteria, are able to stand a more unfavorable environment than the
adult bacteria. Many spores and adults, however, perish. Each kind of
bacterium requires its own special environment to permit it to grow
and flourish. The frequency with which an unfavorable combination of
circumstances occurs limits greatly the disease-producing power of the
pathogenic bacteria.
Many bacteria, moreover, are harmless and do not produce disease, even
when present in the blood and tissues. Besides this, the white blood
cells are perpetually waging war against the bacteria in our bodies.
Pages:
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130