Digestion. 151 



occurring in the digestive canal, the presence of which we 

 recognise by the production of ill-smelling gases. 



In the anterior part of the small intestine no putrefactive 

 odour is obtained, but after the admixture and action of 

 the pancreatic juice a distinctly faecal odour is given to the 

 contents. There can be no doubt of the large number of 

 organisms found in the small intestine, which, to a certain 

 extent, may be useful in assisting digestion, especially that 

 of proteids, and perhaps of fats. By means of organisms 

 also leucin and tyrosin, indol and skatol, lactic and butyric 

 acids, may be formed (Halliburton), and the function of 

 these organisms may further— according to the same ob- 

 server — be protective in destroying poisonous products, 

 such as cholin (the alkaloid derived from lecithin). 



The decomposition of proteids in the large intestine 

 leads to the formation of carbonic acid, sulphuretted 

 hydrogen, ammonia, phenol, kresol, skatol, and certain 

 organic sulphur compounds ; the latter, with phenol and 

 indican, are excreted by the kidneys, and in carnivora and 

 omnivora are regarded as a measure of the putrefactive 

 processes occurring in the bowel. This, however, will not 

 hold good for the herbivora, as the phenol with them is 

 largely derived from the food. 



Phenol, or carbolic acid, is largely formed in the horse, 

 and is excreted by the kidneys. Indol and skatol give to 

 faeces their characteristic odour. 



The longer the food remains in the bowel, the more indol 

 and phenol is formed ; they are decomposition processes, 

 and have nothing to do with nutrition, and are got rid of 

 in flesh-feeders by disinfecting the intestinal canal with 

 calomel. 



According to Tappeiner, phenol is found in the stomachs 

 and intestines of cattle, skatol in the paunch, and indol in 

 the large and small intestines. In the horse, indol is 

 present up to the caecum ; in the colon, its place is taken 

 by skatol. Phenol and ortho-kresol are found throughout 

 the large intestines. 



The fermentation in the intestines of the horse may be 



