DIARRHEAL DISEASES. 133 



ently somewhat the same effect that it has in milk growing 

 in the laboratory, preventing the development of putrefac- 

 tion. If this is true the lactic organisms in the intestine, so 

 far from being the cause of the derangements, are very likely 

 means of checking them. 



A somewhat similar inference may be drawn from recent 

 experiments which indicate that, without the presence of 

 bacteria, normal digestive processes cannot take place (161). 

 If chicks are hatched and fed in such a way as to keep their 

 intestines totally free from bacteria the birds are not properly 

 nourished, cannot handle their food, do not gain in weight 

 and eventually die of poor nutrition. The absence of bac- 

 teria apparently makes it impossible properly to use their 

 food. If there is given with their food a culture of one of 

 the common intestinal bacteria (an acid species) the nutritive 

 functions recover and the birds develop as normal birds. 

 This fact again suggests the beneficial rather than the injuri- 

 ous agency of the lactic bacteria in the intestine, and enforces 

 the conclusion that such bacteria are not only not injurious, 

 but are beneficial, and probably even necessary, in carrying 

 on the normal function of digestion. 



It does not follow from these facts that the presence of 

 great quantities of lactic bacteria in milk is desirable, nor 

 that the larger the number of lactic bacteria in the milk the 

 better the results. We need not draw even the conclusion 

 that the lactic bacteria of milk are necessary for proper 

 digestion, for these experiments may have slightly different 

 interpretations. But it is a safe and legitimate inference that 

 the common lactic bacteria cannot properly be looked upon 

 as the agents for producing the digestive disturbances which 

 are associated with milk bacteria. Diarrheal troubles, if they 

 are due to bacteria of milk, cannot, in the light of the fact? 

 known, be attributed to the common lactic bacteria, and it is 

 quite probable that milk may be filled with bacteria in large 

 numbers, and still be perfectly wholesome as food, provided 



