330 DISTRIBUTION OF BACTERIA 



indol, skatol, hydrogen sulphide, and ammonia. If vegetable 

 material containing a large amount of carbohydrate is acted 

 upon by the bacteria, usually the zymogenic or fermentive 

 processes are predominant, and among other substances 

 organic acids are produced. 



The intestines of carnivorous and omnivorous animals con- 

 tain a greater number of bacteria than the herbivorous animals, 

 and there are considerably more in the large than in the small 

 intestine (De Giaxa). 



It is claimed by certain investigators, among them Gillepsie, 

 that although the majority of bacteria are of no use in gastric 

 or pancreatic digestion, yet some are of great use in controlling 

 putrefaction in the lower parts of the small intestine. Some 

 of the organisms which are able to pass through the stomach, 

 as stated above, produce organic acids during their metabolic 

 activity. These acids, it is claimed, serve to reduce the alka- 

 linity of the contents of the small intestine and consequently, 

 in a measure, control the putrefactive processes due to other 

 bacteria. Saprogenic bacteria are more active in an alkaline 

 than in an acid medium. In the large intestine the alkalinity 

 is so marked that the acids formed by bacteria are of no con- 

 sequence in preventing saprogenic processes. In all proba- 

 bility this action on the part of acid-forming bacteria is of 

 little consequence. They are certainly not necessary auxil- 

 iaries in the process of digestion if they do possibly aid indi- 

 rectly in certain instances. The products of metabolism of 

 the intestinal bacteria for the most part are not in any way 



