INFECTIONS OF THE DIGESTIVE TRACT 51 



spicuous and, as in the rectum, this type has the ap- 

 pearance of being present in pure culture. 



The bacterial flora of the intestinal tract of the nurs- 

 ling is thus only moderately numerous as regards variety. 

 The bacteria are concentrated in the regions that lie 

 between the lower ileum and the anus, the ileocsecal 

 region presenting more kinds of bacteria than the lower 

 colon and more organisms capable of being cultivated. 

 The comparatively small numbers of bacteria found in 

 the small intestine has its explanation partly in the 

 small amount of food that lodges there, partly perhaps 

 in the bacteriolytic action of the succus entericus. 

 Wherever particles of transformed casein are found, there 

 also will be found bacteria in abundance, but with the 

 exception of the lower ileum the small intestine does not 

 harbor food masses to any considerable extent. The 

 bacteriolytic action of the succus entericus is moderate 

 but appreciable. The epithelial cells are said to contain 

 an antitryptic ferment, and this passes to some extent 

 into the succus entericus, where it is perhaps capable 

 of exerting a restraining influence on that peptonization 

 of proteids which is the first essential step toward putre- 

 factive decomposition. 



Various attempts have been made to form a numerical 

 estimate of the numbers of living and dead bacteria 

 present at different levels of the colon and to deter- 

 mine what proportion of bacteria have been rendered 

 lifeless during their descent through the colon. Eberle, 

 who compared the numbers of bacteria seen in micro- 

 scopical preparations with the results of plate cultures, 



