SUMMER DIARRHOEAS OF INFANCY. 137 



found in the intestines of iiifants suifering from summer 

 diarrhoea, and we now find that three species of these are 

 capable of producing chemical poisons, which induce effects 

 substantially identical with the symptoms observed in the 

 infants, and it is not unreasonable to suppose that many 

 other of these germs produce similar poisons. 



(2) Many of these germs are probably truly saprophytic. 

 A germ growing in the intestine does not necessarily 



feed upon living tissue. The food in the duodenum before 

 absorption has no more vitality than the same material in 

 the flask. Moreover, the excretions poured into the intes- 

 tines from the body are not supposed to be possessed of 

 vitality. A germ which will grow upon a certain medium 

 in the flask and produce a poison will grow on the same 

 medium in the intestine apd produce the same poison, pro- 

 vided it is not destroyed by some secretion of the body. 



(3) The only digestive secretion which is known to have 

 any decided germicidal effect is the gastric juice; therefore, 

 if the secretion be impaired there is at least the possibility 

 that the living germ will pass on to the intestine, will there 

 multiply, and will, if it be capable of so doing, elaborate a 

 chemical poison which may be absorbed. 



There is no longer any doubt that the acid of the gastric 

 juice has a marked germicidal effect upon many of the 

 microorganisms. 



Vaughan has found that an exposure to a two-tenths 

 percent, solution of hydrochloric acid for half an hour will 

 destroy Eberth's germ and two poison-producing bacilli 

 which he has isolated from drinking-water which was 

 believed to have caused typhoid fever. Although the ger- 

 micidal effect of this acid has not been tried on the bacteria 

 under consideration, doubtless it will be found to be con- 

 siderable. 



The chief reason why the breast-fed child has a better 

 chance for life than the one fed upon cow's milk lies in the 

 fact that the former gets its food germ-free ; but a second 

 reason is to be found in the larger amount of acid required 

 to neutralize the cow's milk, as has been pointed out by 



