464 



INFECTION AND IMMUNITY. 



they are very susceptible to ordinary antiseptics. 

 The normal serums of many animals are bacterici- 

 dal for the colon bacillus. 



Escherich, the discoverer of this organism, lays 

 down the principle that that strain which may 

 be cultivated from the feces of the nursing child 

 should be considered as the typical Bacterium coli 

 commune, maintaining that a constant type of or- 

 ganism is found under these conditions. It is said 

 to occur here in relatively pure culture. 



Distribution Within a very short time after birth the organ- 

 i sm ^ s found in the intestines of infants, and its 

 method of entrance has been the subject of much 

 discussion. In view of its ready dissemination it is 

 not difficult to conceive of many circumstances 

 which favor its entrance. Having once reached 

 the intestines, it finds there its optimum conditions 

 for growth. The small intestines in man are 

 rather free from colon bacilli and other organisms 

 as well. This, perhaps, is due, to some extent, to 

 the alkalinity of the medium and to the rather 

 rapid flow of the intestinal contents at this point. 

 The colon bacillus reaches its maximum develop- 

 ment in the large intestine, where, in fact, the 

 whole bacterial flora of the intestines is most con- 

 centrated. 



In view of the fact that the colon bacillus is a 

 norma i inhabitant of the intestines, the conception 

 has occurred to many that it may be of distinct 

 value to the economy, either because of the action 

 it has on certain foods (splitting of carbohy- 

 drates), or b'ecause in some obscure way it in- 

 fluences favorably the assimilation of foods, or in 

 that it antagonizes other bacteria of distinct patho- 

 genic powers which also exist normally in the in- 



Normal 

 Functions. 



