GLYCOGEN. 15 



Indol (C G H 7 N) is obtained by digesting large quantities of albumin with 

 ox-pancreas and distilling the product. The distillate contains Indol, which 

 may be separated from it by agitating it with its bulk of ether. Indol fuses at 

 52 C. and boils at 245 C. It is soluble in water, and crystallizes from its 

 solution in shining plates. When introduced into the circulating blood or 

 alimentary canal, an "indigo-producing substance " appears in the urine. It 

 exists, under normal circumstances, in extremely small quantity in the in- 

 testinal contents. 



Skatol, a crystallizable body of offensive odour, resembling Indol, has been 

 lately discovered by Brieger as a constituent of human faeces. It has also 

 been shown that Phenol (Carbolic Acid, C 6 H 5 , OH) is constantly present in 

 fseces. 



An alkaline liquid, called Succtis entericus, of low specific 

 gravity, is secreted by the mucous membrane of the small 

 intestine. Its digestive properties are as yet uncertain. 



Glycogen. 



Glycogen, or animal starch, is under normal conditions 

 always present in the living cell-substance of the liver ; in 

 inanition it gradually disappears ; it is present in the livers 

 of animals fed exclusively on flesh. The glycogen of the 

 liver increases after each period of digestion. Its quantity 

 is in general determined by the quantity of dextrose-pro- 

 ducing material or of lactose in the food, so that these 

 sugars are the normal but not the only source of glycogen. 

 The processes by which glycogen disappears from the liver 

 in inanition, and by which it is normally disintegrated in 

 the animal organism, are not known. After death, the 

 glycogen of the liver is converted into dextrose under the 

 influence of a diastatic ferment. 



Glycogen or animal starch is soluble in water, yielding an opalescent solu- 

 tion. It is coloured brown or reddish-brown by iodine. Glycogen is ob- 

 tained in quantity, by throwing the rapidly comminuted liver of an animal 

 just killed, during the period of greatest digestive activity of the organ, into 

 boiling water slightly acidulated with acetic acid. ..From the pale yellow 

 filtered and concentrated extract, glycogen is precipitated by the addition of 

 alcohol. 



