698 ARTHUR ISAAC KENDALL . 



that fully eighty per cent of the bacteria seen in the feces are dead of 

 so weakened in vitality that they can no longer be cultivated in artificial 

 mediums. In other words, the most intense bacterial proliferation is in 

 the lower ileuni, the ceeum, and the ascending colon. 



The types of bacteria vary at the different levels. In the duodenum 

 and jejunum, where the carbohydrates are ordinarily abundant during 

 digestive periods, the amylolytic bacteria those which thrive best where 

 starches are present are found in dominating numbers. 21 At the lower 

 levels, facultative bacteria, as Bacillus coli which can grow well upon 

 a carbohydrate or upon a protein diet are found to be the principal 

 types. The carbohydrophilic bacteria are carried to these levels with the 

 downward passage of the intestinal contents, but gradually decrease in 

 numbers as well as activity with the diminution of the sugar content of 

 the intestinal medium. 



In the cecum a considerable number of types of bacteria are found, 

 chiefly those which thrive upon a protein regimen. Starches appear 

 to play a minor part in determining bacterial types, especially in the 

 lower levels of the alimentary canal; the products of hydrolysis of the 

 ordinary starches are glucose, and polymers of glucose. These are not 

 liberated in considerable amounts at any one time, and the soluble products 

 of hydrolysis are usually absorbed relatively rapidly. Under these con- 

 ditions the effect of starches upon intestinal bacterial metabolism, par- 

 ticularly with reference to their sparing action for protein, is not great. 

 The observation of Torreyis that fats do not apparently play a prominent 

 part in the nutrition of intestinal microbes. 



It is not difficult to advance an explanation of the sudden rise in 

 indican when an intestinal obstruction is created. In such cases, car- 

 bohydrate is removed more rapidly from the intestinal contents than the 

 protein, leaving a nitrogenous pabulum for the bacteria. The gradual 

 filling of the intestines to the higher levels encourages a corresponding 

 extension upward of the habitat of the indol-forming bacteria of the 

 colon type and the periodic emptying of the duodenum no longer is a 

 factor in sweeping down the organisms which are resident there. The 

 net result is an upward extension of the putrefactive flora, and an aug- 



* Surgical operations involving the small intestine are said to be less frequently 

 complicated by bacterial infection than those of the large intestine. The suggestion 

 is offered that the microbes of the upper small intestine are not only fewer in numbers 

 but are also lactic acid producing, and therefore fermentative rather than toxicogenic 

 in their activities. Whatever of carbohydrate (starch or sugar) there may be in 

 the food is absorbed chiefly from the intestines not from the stomach (Howell) 

 and therefore the upper levels are periodically or even constantly bathed in this group 

 of non-nitrogenous substances. In the interdigestive periods the food passes downward, 

 carrying a majority of the bacteria with it. This appears to be an explanation of the 

 prominence of acidogenie bacteria in the duodenum. 



At the lower levels, the normal adult intestinal flora is facultative with reference 

 to proteolysis; such organisms are more commonly found to be incitants of infection 

 than the more strictly or obligately acidogenic forms. 



