404: DIGESTION. 



garde constituents of bone, etc. The faeces sometimes contain 

 a small quantity of fatty acids. 



The inorganic matters contained in the faeces consist 

 chiefly of the phosphate of magnesia, with the phosphate of 

 lime and a little iron. "When the reaction is neutral or 

 alkaline, crystals of the ammonio-magnesiaii phosphate are 

 found. Mucus exists in the faeces in small quantity, with epi- 

 thelium and a few leucocytes. 



The only characteristic excrementitious constituents of the 

 faeces which have yet been described are : stercorine, the 

 most important excrementitious principle discharged by the 

 rectum, and excretine and excretoleic acid, which have been 

 found as yet only in the human faeces. Though the color of 

 the faeces is undoubtedly due to a transformation of the col- 

 oring matter of the bile, neither the biliary salts nor biliver- 

 dine are to be detected in the large intestine by the ordinary 

 tests. The coloring matters of the faeces resemble the color- 

 ing matters which have been extracted from the blood and 

 the urine. 



Movements of the Large Intestine. Movements of the 

 same general character which we have noted in the small 

 intestine occur in the large intestine ; though the peculiari- 

 ties in the arrangement of the muscular fibres and the more 

 solid consistence of the contents render these movements 

 somewhat distinctive. In all instances where these move- 

 ments have been observed in the human subject or the lower 

 animals, they have been found to be less vigorous and rapid 

 than the contractions of the small intestine. Indeed, when 

 the abdominal organs are exposed, either in a living animal 

 or immediately after death, movements of the large intestine 

 are generally not observed, except on the application of me- 

 chanical or galvanic irritation ; and they are then more cir- 

 cumscribed -and much less marked than in any other part of 

 the alimentary canal. In the rabbit, in which the colon is 

 very large, the few spontaneous movements which are some- 



