THE BACTERIA (SCHIZOMYCETES) 165 



numbering 281,500,000,000, and "in three days the progeny 

 of a single cell would balance 148,356 hundredweight." ^ Of 

 course it is well known that ordinarily this rate of reproduc- 

 tion cannot be realized, because growth conditions do not 

 remain favorable. The food supply is soon exhausted, and 

 the excretions from the bacteria themselves render conditions 

 unfavorable. But in situations where bacteria can grow they 

 really do reproduce themselves and increase their number 

 with astonishing rapidity. The possibilities of production and 

 growth of large numbers are evident when we keep in mind 

 that for a considerable time many millions of bacteria could 

 live in a cubic inch of milk or beef broth. 



In another kind of reproduction that is found in but a 

 few of the bacteria the interior of the bacterial cell becomes 

 rounded and inclosed by a relatively heavy wall. This heavy- 

 walled body may remain inactive for a long period, and upon 

 the return of favorable conditions may again produce the kind 

 of cell which formed it. Such specially made reproductive 

 cells are called spores. They often serve to preserve bacteria 

 through periods of unfavorable conditions, — as drought, lack 

 of proper air, absence of suitable food, and unfavorable tem- 

 perature. Some kiiads can ^\-ithstand freezing or boiling tem- 

 peratures. It is much more difficult to destroy bacteria that 

 produce spores than those which have only the usual growing 

 structures. There are very few spore-forming bacteria among 

 those that produce diseases of men. This is fortunate for men, 

 since the problem of combating disease would be much more 

 complex if all our disease-producing bacteria should possess 

 these resistant spores. 



An illustration of bacterial spore action is seen in the disease 

 known as anthrax. Sometimes sheep, cattle, rats, mice, and 

 other animals, as well as men, are killed within a very short • 

 time — a few hours to a few days — by this disease. Before 

 adopting the method of treatment devised by Louis Pasteur, 

 France, in single years, has lost as much as S20, 000,000 

 1 Jordan, E. 0., General Bacteriology, 1908, p. 61. 



