THE SUMMER DIARB,H(EAS OF INFANCY. 93 



the proteid, and these remained sterile, thus demonstrating that no 

 germ was introduced into the animals along with the chemical 

 poison. 



The following conclusions concerning the germs which cause the 

 summer diarrhoeas of infancy may be formulated : 



1. There are many microorganisms, any one of which, when intro- 

 duced into the intestines of the infant, under certain favorable con- 

 ditions may produce diarrhoea. 



2. Many of these microorganisms are true saprophytes. 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 a culture flask. Moreover, the excretions 

 poured into the intestines from the body are not possessed of vitaUty. 

 A bacterium which will grow upon a certain medium in a flask and 

 produce a poison will grow on the same medium in the intestine and 

 produce the same poison, provided it is not destroyed by some secre- 

 tion of the body. 



3. The only digestive secretion which is known to have any de- 

 cided germicidal effect is the gastric juice ; therefore, if this 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. It 

 has been said that the gastric juice does not act as a germicidal 

 agetit, because there are other acids which are more powerfully bac- 

 tericidal than hydrochloric acid, but there is no force in this argu- 

 ment. The question is not whether the stomach is supplied with the 

 very best germicide, but whether it is supplied with any at all. The 

 human eye is not by any means a perfect mechanism, but it is man's 

 only organ of vision. 



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 

 large amount of acid required to neutralize the cow's milk, as has 

 been pointed out by Escherich. It is also possible that some of the 

 secretions poured into the intestines have germicidal properties, or 

 that the cells, in absorbing the bacterial proteids, may to a limited 

 extent so alter them that they are no longer poisonous, or that in a 

 perfectly normal condition the liver may be able to prevent these 

 poisons from entermg the general circulation without change. 



4. Any germ which is capable of growing and producing an ab- 

 sorbable poison in the intestines may, for all practical purposes, be 

 considered pathogenic. It is not necessary that a bacterium be cap- 

 able of growing and causing disease and death when injected under 

 the skin or into the blood in order to establish its right to rank 

 with the pathogenic germs. In the blood the organism is acted 

 upon by a wholly different fluid from that by which it is surrounded 



