CHAPTER XL 



IMPURE FOOD AND AIR AS SOURCES OF BAC- 

 TERIAL INFECTION. 



AS we glance back over the ground which 

 we have traversed together, we see that 

 the most common bacterial diseases which in 

 this country we are apt to come in contact 

 with, so far as they are definitely known to us, 

 are tuberculosis, typhoid fever, diphtheria, 

 pneumonia, and the wound diseases or blood 

 poisoning. 



We have seen that in most of these diseases 

 the poison is liable to spread from one indi- 

 vidual to another, because it is not destroyed 

 by disinfectants, or in some other way, as soon 

 as possible after it is discharged from the dis- 

 eased person. 



We have seen that the most common ways 

 in which the virulent bacteria are spread are 

 by the air we breathe, the food we eat, and 



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