564 



STORAGE OF GLYCOGEN. 



[BOOK ii. 



to no accumulation of glycogen in the liver ; an animal fed on 

 an exclusively fatty diet has no more glycogen in its liver than 

 a starving animal. 



Hence of the three great classes of food-stuffs, the carbo- 

 hydrates stand out prominentty as the substances which taken 

 as food lead to an accumulation of glycogen in the liver. We 

 may remark that the greatest accumulation of glycogen is 

 effected not by a pure carbohydrate diet, but by a mixed diet 

 rich in carbohydrates. A quantity of carbohydrate mixed 

 with a certain proportion of proteid gives rise to a larger 

 amount of glycogen in the liver than the same quantity of 

 carbohydrate given by itself ; and it is possible that the pres- 

 ence of an appropriate quantity of fat still further assists the 

 accumulation. But this result probably depends, in part at 

 least, on the fact that, though differences may be met with in 

 different animals, a mixture of the several classes of food-stuffs 

 is more readily digested resulting in more nutritive material 

 being thrown upon the blood, than is a meal consisting exclu- 

 sively of one kind of food-stuff alone. 



So far as we know at present the glycogen which thus 

 appears in the liver as the result of feeding either with any of 



FIG. 105. SECTION OF LIVER OF FROG. (Langley.) 



The Figure shews the tubular structure of the liver. At (a) a tubule ia 

 seen in transverse, at (6) in longitudinal section. I, lumen of tubule. 



The liver was that of a winter frog, and the cells shew an inner zone of 

 proteid granules ; the outer zone was chiefly occupied by glycogen. 



