THE BACTERIA 203 
and, upon the return of favorable conditions, may grow and 
produce the kind of cell which formed it. Such specially pro- 
duced reproductive cells are called spures. They often enable 
the bacteria and other plants to live through periods of un- 
favorable conditions — as drought, lack of proper air, absence 
of suitable food, and unfavorable temperature. Some kinds 
ean withstand freezing or boiling temperatures. It is much 
more difficult to destroy the spores of bacteria than the vege- 
tative, or growing, cells. There are very few spore-forming 
bacteria among those that produce diseases of men. This is 
fortunate, since the problem of combating disease would be 
much more complex if all the harmful bacteria should be able 
to form these resistant spores. A disease known as anthrax 
offers a good illustration of the way in which spore formation 
may increase the distribution of disease. .Anthrax is a very de- 
structive disease, as is shown hy the fact that, prior to the use 
of the treatment devised by Louis Pasteur, France in single 
years has lost as much as $20,000,000 worth of cattle and 
sheep. The disease also affects men and may cause their 
death, as it does that of cattle, sheep, and other animals, in 
from a few hours to a few days after infection. The spores of 
anthrax form only when the bacteria are exposed to the air. 
When an animal dies of anthrax, if its body decays while ex- 
posed to the air, millions of anthrax spores are formed. These 
spores can lie in the field for very long periods, probably 
several seasons, and withstand the variations in temperature, 
moisture, and light. When they are introduced into the ali- 
mentary tract of an animal, they soon reach the circulatory 
system, where they grow with surprising rapidity and may 
soon cause the death of the newly infected animal. The de- 
sirability of the complete destruction of bodies of animals that 
have died of anthrax is evident. 
190. Bacterial decay and its significance. The bacteria and 
certain other dependent organisms (as molds, yeasts, and 
many animals), while living upon the bodies or the products of 
plants and animals, use parts of them as food. The processes 
