PUTREFACTIVE FERMENTATIONS IN THE INTESTINE. 191 



reduces the consistence of the faeces and facilitates the evacuation. 

 The fsetor depends in a great measure on the presence of indol, 

 which is an outcome of pancreatic digestion, and also upon the 

 presence of certain volatile fatty acids. The color depends upon 

 the amount of the bile pigment and the degree of change the 

 latter has undergone. 



The faeces are composed of (1) the undigested parts of the food, 

 and (2) the useless or injurious parts of the secretions of the 

 various glands. In the first category we find perfectly indiges- 

 tible stuffs such as yellow elastic tissue, horny structure, portions 

 of hairs from animal food, and cellulose, woody fibre and spiral 

 vessels from plants, and also masses of digestible substances 

 which have been swallowed in too large pieces to be thoroughly 

 acted on by the secretions. All forms of food may thus appear 

 in the fseces, but most commonly vegetable substances are con- 

 spicuous. 



In the second category we find a variable quantity of mucus 

 and the decomposed coloring matter of the bile together with 

 some cholic acid, cholesterin, etc. 



A few inorganic substances are found, mainly those which dif- 

 fuse with difficulty, as calcium salts and ammonio-magnesium 

 phosphate. 



Putrefactive Fermentations in the Intestine. 

 With the air and saliva which are swallowed mixed with the 

 food, large numbers of the lower organisms existing in them are 

 introduced into the alimentary canal. 



The effect of these organisms is to produce certain fermentative 

 changes quite distinct from the action of the special ferments 

 peculiar to the digestive fluids. 



This is proved by the composition of the gases found in the 

 intestine. Atmospheric air only is introduced from without, and 

 this is not found in any part of the alimentary tract, the oxygen 

 soon being absorbed and the nitrogen left, while a quantity of 

 carbonic anhydride and hydrogen from the fermentation of the 

 sugar are set free, lactic and butyric acids being produced at the 

 same time. 



Indol and skatol are also formed by putrefactive fermentation 



