Chapter V 
THE MICROBES THAT MAKE US SICK 
M ICROBES of certain kinds cause disease. 
These microbes that make us ill are 
those whose food is living animal tissue, and 
that carry on their life and multiply in the 
bodies of animals and human beings. By their 
feeding on the substances of the body, they are 
capable of causing many different kinds of 
illness. Some can live in the bodies of animals 
without doing any harm, but when they get 
into the bodies of human beings they cause 
serious injury. Other kinds hurt only one part 
of the body and cause no harm in other parts, 
or they attack only at certain favorable times. 
Some disease germs spread all over the body; 
they grow rapidly in the blood and tissues. In 
such cases the disease caused by their attacks is 
not centered at any particular point, but is at 
What microbes 
cause sickness? 
63 
