THE CHEMISTRY OF THE ANIMAL BODY IGl 



but soluble in alcohol, chloroform, or alkalies. It is found 

 especially in the bile of the carnivora, and by exposure to ai! 

 in alkaline solution absorbs oxygen and passes into hiliverdin, 

 CjgHjgNgO^, an amorphous green substance, insoluble in water, 

 but soluble in alcohol and alkalies. This substance is found 

 in bile and in the shells of many birds' eggs. 



Bile has a slight power of dissolving fats (a familiar appli- 

 cation of this is afforded by the use of ox-gall for removing 

 grease, &c., from carpets and other textile fabrics), and has a 

 distinct antiseptic effect upon the contents of the intestines. 

 Bile is to a large extent reabsorbed in the intestines. 



In the intestines many chemical changes occur, many being 

 induced by bacteria, which grow freely in the alkaline contents, 

 producing various putrefactive decompositions. Carbohydrates 

 produce lactic acid, cellulose splits into carbon dioxide and 

 marsh gas, while butyric acid, C3Hy.C00H, and valeric acid, 

 C^Hg.COOH, result from the bacterial hydrolysis of fats. Two 



characteristic substances — indol, CgH^^ /CH, and sJcaiol, 



^NH/ 



or methyl indol, CgH^^ /CH, crystalline substances 



^ NH / 

 with very unpleasant odours, have been extracted from the 

 contents of the intestines, and it is to the presence of these 

 substances that the unpleasant smell of faeces is largely due. 



Destination of Digrested Food.— Some few constituents 



of the food can be absorbed without undergoing chemical 

 changes ; this is the case with water and common salt, perhaps 

 also with some soluble proteids. Absorption commences in 

 the stomach, but is mainly accomplished in the intestines by 

 the lacteals and lymphatics. 



The carbohydrates are probably entirely absorbed in the 

 form of maltose or glucose, being converted into these com- 

 pounds by the enzymes of the saHva, pancreatic juice, and 

 intestines. Some of these enter the blood stream and are 



