OUTPUT OF WASTE MATTER 139 



matters, chiefly phosphates, found in the 

 faeces. Finally a large portion of dried 

 faecal matters consists of bacteria, which 

 have already been referred to as existing 

 in enormous numbers in the alimentary 

 canal. 



72. There is still another organ which, from 

 one point of view, may be regarded as excre- 

 tory, namely the liver. A portion of the bile 

 is undoubtedly thrown out in the faeces, but 

 others matters are re-absorbed and return to 

 the liver. This organ is the seat of numerous 

 chemical and vital processes that are in a 

 sense hidden. These will be further con- 

 sidered. 



73. The bile is an alkaline fluid containing 

 usually a large amount of a mucus-like matter, 

 which gives it a peculiar " ropy " character 

 when poured from one vessel into another. It 

 contains two nitrogenous pigments, bilirubin 

 and biliverdin. In the bowel bilirubin is 

 robbed of oxygen by reduction processes and 

 becomes the pigment of the faeces, stercobilin. 

 Part of the latter may be re-absorbed, and is 

 then eliminated in the urine as urobilin, one 



