724 STORAGE OF GLYCOGEN. [BOOK n. 



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 to very 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. Further, in certain cases of the disease diabetes, 

 of which we shall have to speak presently, and which is charac- 

 terized by the presence of a large amount of sugar in the blood, 

 sugar continues to be formed in large quantity, even when the 

 diet is entirely restricted to proteid and fatty matters, all carbo- 

 hydrates being excluded. Now in diabetes we have reason 

 to believe that the large quantity of sugar in the blood is 

 accompanied by a large deposition of glycogen in the liver, and 

 indeed in other tissues ; for in the few cases which have been 

 examined sufficiently soon after death, and in which owing to the 

 suddenness of the death, then- was m opportunity for stored-up 

 glycogen to disappear, a very large quantity of glycogen has been 

 found in the liver or in some other organs.4 Hence the phenomena 

 of diabetes may be taken as shewing, in a much more striking 

 manner than do any experiments, that proteid material taken as 

 food may give rise to hepatic glycogen. And this at first sight 

 seems to afford proof that the hepatic glycogen is a product of 

 the metabolism of the hepatic cell, the activity of the cell being 

 stimulated as it were by the presence of the proteid food. But 

 the proof is not cogent in the face of our ignorance of the meta- 

 bolic changes which the proteid material of food undergoes in the 

 body. As we shall insist upon in more detail later on, proteid 

 material in giving rise to urea throws off somewhere in the 

 body a large quantity of a carbon-containing radicle in some 

 combination or other ; the proteid contains far more carbon than 

 is needed to unite with the nitrogen to form urea. We shall 

 see that this excess of carbon has a tendency to appear in the 

 form of fat, but we may readily suppose that it might temporarily 

 as a preliminary process or under certain circumstances take on 

 the form of sugar. And we may further suppose that the sugar is 

 formed out of the proteid not in the liver but in some other tissue, 

 in muscle for instance. But if so, hepatic glycogen which is the 

 result of proteid food, may after all be formed in the liver by 

 simple dehydration of sugar formed elsewhere, and brought to the 

 liver in the portal blood. 



We cannot, we say, at present decide between these two views; 

 and indeed it may be that both views are true, or rather that the 



