DIGESTION 265 



the faeces of many animals in Arctic regions are free 

 from them. Nor is the number or character of the 

 bacteria in the faeces very different in animal and 

 vegetable feeders,* or whether the diet be an ordinary 

 mixed or a purely vegetarian one. 



The characteristic organisms of the small intestine 

 are those which produce acids from carbohydrates ; that 

 of the large intestine, the Bacillus coli. Putrefactive 

 bacteria are not found to any extent in the ileum, and 

 the contents of the latter, even at its lower end, contain 

 no putrefactive products such as leucin, tyrosin, 

 indol, or skatol.t Hence they are also devoid of faecal 

 odour. 



In the ileum bacteria are present in greatest number 

 at the lower end the restraining power of the gastric 

 juice being apparently still operative higher upt and it 

 is interesting to remember that it is just this part of the 

 bowel which is most subject to infective disease. 



The acids produced by the acid-forming bacteria tend 

 constantly to be neutralized by the alkaline secretion 

 of the pancreas and intestine, but in spite of that the 

 activity of acid production is sufficient to give the con- 

 tents of the ileum a slightly acid reaction, which tends 

 to restrain putrefaction. Hence a diet which contains 

 much carbohydrate is one on which little intestinal 

 putrefaction can occur. 



In the colon putrefactive organisms get the upper 



* Levin, abstract in Archiv f. VerdauungskranJch, 1904, x. 530. 

 f Neucki, etc., loc. cit, 



% Lorrain Smith and Tennant, Brit. Med. Journ., 1902, ii. 1941. 

 Backman, Zeit.f. Klin. Med., 1902, xliv. 458. 



