DIARRHEAL DISEASES. 13! 



troubles would be due to growth of bacteria in the intestine. 

 It is also possible that both of these methods may be con- 

 cerned. The bacteria may develop in the milk both previous 

 to and after its consumption, and the toxic products may be 

 produced in both places. Lastly it is possible that the bac- 

 teria may themselves invade the tissues of the person and 

 develop in some organs outside of the intestinal tract. We 

 do not yet know which of these methods is the more com- 

 mon, although it is probably not the last. 



Type of Bacteria Producing these Diseases. Our knowl- 

 edge in regard to the actual cause of such intestinal troubles 

 is thus rather meager. It is true that large numbers of bac- 

 teria have been found in the intestines of children suffering 

 from such troubles. These have been described by bacteriol- 

 ogists, but the results of such study have not been to disclose 

 the cause of the diseases. Nevertheless, some few general 

 facts are suggestive of the type of bacteria which are most 

 likely concerned. 



It seems probable that the intestinal disturbances must be 

 in part attributed to that class of bacteria which we have 

 called the putrefactive bacteria or pcptonizing bacteria; the 

 group that produce albuminoid decomposition and give rise 

 to a variety of by-products. On the other hand, it is almost 

 certain that the common lactic bacteria (Bact. lactis acidl 

 and its allies) cannot be accused of producing these troubles. 

 In earlier years it was thought probable that the immense 

 development of lactic bacteria in the milk rendered the milk 

 unwholesome. They cause the milk to become acid, and this 

 acidity has frequently been regarded as the cause of intestinal 

 troubles. At the present time, however, the evidence is 

 against such a view and there is good reason for believing 

 that lactic bacteria, so far from being the cause of such 

 intestinal disturbances, must be looked upon as protecting 

 the milk from development of other bacteria that would be 

 more injurious to the consumer. 



