148 PRINCIPLES OF PHYSIOLOGY 



it is used up in the chemical processes occur- 

 ring in that tissue connected with contraction. 

 During the intervals between absorptive 

 periods, and while no carbo-hydrate is derived 

 from the bowel, the muscles still require 

 carbo-hydrate, and this they obtain from the 

 store of glycogen stored in the hepatic cells. 

 How the glycogen is removed from the cells, 

 and again re-transformed into sugar, either 

 in the hepatic cells, or in the colourless cor- 

 puscles, or in the muscular tissues themselves, 

 has not yet been clearly explained. Probably 

 again enzyme action is called into play. 

 Another enzyme has been found in the liver, 

 capable of transforming the glycogen into 

 sugar, and various sugar-forming substances 

 have been found in muscle. There appears to 

 be in muscle, especially at an early stage 

 of development, a variety of glycogen, or 

 carbo-hydrate destined for its nutrition. The 

 phenomena that occur in the hepatic cell 

 are unknown. It is possible, as already sug- 

 gested, that the transformations in protein 

 matter, as well as in carbo-hydrate matter, 

 may be one intricate chemical operation a 



