224 BIOLOGY AND TECHNIQUE 



a considerable extent dependent upon diet. Also, many of the bac- 

 teria that cause specific diseases of the intestinal canal, such, for 

 instance, as the typhoid bacillus, the paratyphoid bacilli, the dysen- 

 tery group, and some of the doubtfully pathogenic organisms like 

 the Morgan bacilli, are very closely related in morphology and cul- 

 tural reactions to non-pathogenic and saprophytic inhabitants of 

 the bowel. In no type of bacteriological work, therefore, is it more 

 necessary to have an intelligent understanding of the bacterial 

 species that are likely to be found without pathogenic significance. 



Furthermore, the intestinal canal is a large test tube from which 

 bacterial products can be absorbed in sufficient amounts to cause 

 severe illness. In it, different kinds of food supply nutritive ma- 

 terial which may favor one or another species, and various condi- 

 tions of aerobiosis and anaerobiosis may prevail. It is more than 

 likely, therefore, that many so-called cases of intestinal poisoning, 

 formerly loosely spoken of as ptomain poisoning, may be caused 

 by substances formed within the intestine by bacterial action upon 

 the food, rather than upon the relatively smaller amount of fermen- 

 tative and putrefactive products taken in. with partially decomposed 

 food. 



The intestinal canal of the child at birth is sterile. The meconium 

 of such children has been found by many investigators to be free 

 from bacteria. But this does not last very long. Within a few 

 hours after birth, infection takes place, and from then until death, 

 the intestinal canal is constantly the seat of a voluminous and varied 

 bacterial life. Kendall, 14 who has written much on this subject, 

 and in his book has brought together much of the information, 

 gathered from the researches of Escherich, 15 Herter, 10 and his own 

 investigations, has classified the different stages of the bacterial flora 

 in man, as follows: 



1. Bowel at birth, sterile. 



2. First to the third day a period of " adventitious bacterial in- 

 fection.'' 



After this time there is the period of establishment of the charac- 

 teristic infantile intestinal flora which gradually changes as the diet 



"Kendall, Bacteriology, General, Pathological and Intestinal, Lea & Febiger, 

 Phila., 1916, p. 580. 



15 Escherich, Darmbakterien des Sauglings, Stuttgart, 1886, p. 9. 



18 Herter, The Common Bacterial Infections of the Digestive Tract, Harvey 

 Lect., 1906-1907. 



