CHAPTER III 
BACTERIA 
WHAT THEY ARE 
THEY are vegetables. They are the smallest 
of all plants. Twenty-five thousand bacteria end 
to end would cover a distance of I inch. They 
are so small that it takes a powerful magnifying 
glass to see them. They have no roots and no 
leaves. Some of them are shaped like cucumbers, 
and others like oranges. 
Most large plants, such as trees and corn and 
wheat, are harmless. A few are poisonous, such 
as poison ivy, mushrooms and sumach. Among 
bacteria there are hundreds of kinds entirely 
harmless, but a few are poisonous, such as typhoid, 
tuberculosis, sore throat and diphtheria. The 
poisonous bacteria have learned to grow in the 
warm and moist climate of human and animal 
bodies. There they make poisons which cause 
diseases known by their names. 
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