MICROBES IN THE HUMAN BODY 35 



enterococci, mesentericus and an acidophilus. After the third 

 day the flora becomes more simple, being dominated by one 

 of the last to appear, the anaerobe B. bifidus of Tissier, which 

 is characteristic of the flora of the healthy breast-fed infant ; 

 along with it persists the Bacillus coli, the enterococcus and 

 the B. lactis aerogenes. Thanks to the presence of B. bifidus 

 and the lactic bacilli, which produce acids from the carbo- 

 hydrates (human milk is rich in sugar especially after the 

 tenth day), the putrefying bacteria (B. perfringens, for example) 

 are kept in check or even entirely eliminated. Proceeding 

 from the stomach to the rectum the species which predominate 

 in turn are the B. coli, the B. lactis aerogenes, the enUrococcus^ 



% % .* *\ m 



FIG. II. Bacteria in the FlG. 12. Bacillus sporogsnes 



feces of a normal child of (Metchnikoff). 



19 months. 



the B. exilis, the B. acidophilus and lastly the B. bifidus. The 

 distribution and proportions may be altered in the case of the 

 infant not breast-fed. The chemical surroundings being 

 different, the fermentations also differ. 



From the age of one to five years and in particular after 

 weaning, the flora has added to it several new species, while 

 still retaining the species found in the infant, which may be 

 regarded as the fundamental flora. Tissier calculates the pro- 

 portion of this fundamental flora in the child brought up on a 

 vegetable diet at 90 per cent, of all the bacteria and J of 



D 2 



