34 PHYSIOLOGICAL CHEMISTRY. 



It is probably through this glycogen that the muscle is capa- 

 ble of doing its work. Through enzymic hydration the gly- 

 cogen becomes sugar, possibly maltose and then glucose, and 

 the potential energy of this is liberated by oxidation to water 

 and carbon dioxide ultimately. The oxidation may not be 

 direct ; in all probability there are several transformation prod- 

 ucts before the final stages are reached. But the energy trans- 

 formation is the same whatever the intermediate steps may be. 

 The importance of the glycogen and related bodies in this 

 direction will be pointed out in a following chapter. It may 

 be recalled that in these oxidation processes, where sugar is 

 concerned, a muscle enzyme and a pancreas enzyme seem to be 

 both necessary. 



While glycogen in the muscles must come mostly from 

 sugars, either directly or through the liver, there is also some 

 evidence that it may come in part from other substances, espe- 

 cially from proteins. Animal experiments have shown ap- 

 parently a storing of glycogen from a protein diet after pre- 

 vious starvation had exhausted the reserve in store. In the 

 breaking down of some proteins it has been shown that certain 

 carbohydrate groups are liberated; it is doubtless these which 

 undergo synthesis to form at least part of the glycogen, and 

 from this standpoint the behavior of protein as a glycogen 

 factor is not so hard to understand. 



The glycogen content of the muscles of different animals 

 is variable; in the flesh of the horse it is relatively high, 

 amounting often to over i per cent. As the muscle glycogen 

 is not altered rapidly in the dead organ, as is the liver glyco- 

 gen, the presence of the substance in horse-flesh sausage may 

 be quite readily recognized. Methods have been devised for 

 the identification of horse-flesh, sold for food, based on these 

 facts. Glycogen may be extracted from the muscles by the 

 general method given for the liver in an earlier chapter; the 

 chemical and optical properties may be used for the final iden- 

 tification. 



INOSITE. This substance has the .empirical formula 



