758 STORAGE OF GLYCOGEN. [BOOK n. 



products of the hepatic metabolism are stored up as glycogen. 

 Under such a view the sugar of the meal is used up somewhere 

 in the body, and the glycogen to the storage of which in the 

 liver it gives rise comes direct from the hepatic substance. And 

 a similar explanation may be given of the storing-up of glycogen 

 in the liver under such circumstances as those of the winter frog 

 previously mentioned. 



We do not possess at present experimental or other evidence 

 of so clear a kind as to enable us to decide dogmatically between 

 these two views ; we are limited for the most part to general 

 indications. We have seen that proteid food, though in this respect 

 falling far below carbohydrate food, does or may give rise to a 

 certain amount of glycogen in the liver; and gelatin seems to have 

 the same effect. 



In such cases of course the glycogen in the liver must be formed 

 in some way other than by the simple dehydration of sugar coming 

 from the alimentary canal. Now we have evidence in various ways 

 that proteid material taken as food may, through the changes 

 which it undergoes in the body, give rise to sugar. As we shall 

 explain in more detail later on, proteid material on its way to 

 become urea, in the form of which substance the whole of its 

 nitrogen, broadly speaking, is discharged from the body, throws off 

 from itself some constituent (or constituents) rich in carbon; 

 the proteid contains far more carbon in proportion to the nitrogen 

 than does urea. We shall further see reasons for thinking that 

 this carbon-holding product if it be not immediately oxidized may 

 be retained within the body in the form of fat ; but we have also 

 evidence that it may take on the form of sugar. For instance in 

 certain cases of the disease diabetes, of which we shall speak 

 presently and which is characterized by the presence in the blood 

 of an abnormally large amount of sugar, sugar continues to be 

 formed in the body and to be discharged in the urine in very 

 considerable quantities, even when the diet is restricted to proteids 

 and fats or even to proteids alone, all carbohydrates being excluded ; 

 in such cases the sugar must be derived from proteid material. 

 Further, in such cases a certain proportion may be observed to 

 be maintained between the amount of sugar discharged by the 

 urine and the amount of urea present in the same urine, indicating 

 that, as we said above, the proteid material is somewhere in the 

 body split up into urea (or its antecedent) and into sugar. And 

 there are other facts pointing in the same direction. 



Now we may suppose that such a splitting up of proteid 

 material takes place in the liver under ordinary circumstances 

 as part of the normal metabolism of the hepatic cell, the sugar so 

 formed being, according to the demands of the rest of the body, either 

 discharged from the liver as sugar or stored up in the substance of 

 the hepatic cells as glycogen, and on this we may base an argument 

 tending to decide whether the glycogen which is formed in the 



