PHYSIOLOGY OF THE LIVER AND SPLEEN. 755 



clinical experience upon human beings suffering from diabetes. 

 In severe forms of this disease the carbohydrate material of the 

 food escapes oxidation in the body and is secreted unchanged in 

 the urine. If under these conditions the individual is given an 

 exclusively protein diet sugar still continues to appear in the urine, 

 and it would seem that this sugar can only arise from the protein 

 food. In the similar condition of severe glycosuria that may be 

 produced by the use of phld'ridzin it has been shown that the animal 

 continues to excrete sugar even when fed on protein alone or when 

 starved. Under such conditions the amount of dextrose in the 

 urine bears a definite ratio to the amount of nitrogen excreted 

 D : N : : 3.65 : 1 (Lusk), which would indicate that both arise from 

 the breaking down of the protein molecule. On this supposition 

 58.4 per cent, of the protein may be converted to sugar. So also 

 the fact that during prolonged starvation, lasting for forty or even 

 ninety days, the blood retains a practically constant composition 

 in sugar indicates that this material is being formed from either 

 the protein or fat supply of the body. Other considerations tend 

 to exclude the fat, and we are, therefore, led to the belief that the 

 protein can give rise to sugar in the body. If this change is part 

 of the normal metabolism of the body it would make protein a gly- 

 cogen-former, since the sugar formed from the protein may, of course, 

 be converted to glycogen. Whether or not all proteins yield gly- 

 cogen or sugar in the body is not entirely determined. Some 

 authors have thought that only those proteins that contain a 

 carbohydrate residue have this property; but, as stated above, 

 casein and other proteins that do not possess this grouping seem 

 also to increase the glycogen supply when fed alone. 



Effect of Fats upon Glycogen Formation. A large number of 

 substances have been found by some observers to increase the store 

 of glycogen in the liver. In some of these cases at least it is evident 

 that the substance is not a direct glycogen-former in the sense that 

 the material is itself converted to glycogen. It may increase the 

 supply of liver glycogen in some indirect way, for example, by 

 diminishing the consumption of glycogen in the body. The most 

 important substance in this connection from a practical standpoint 

 is fat. Whether or not the body can convert fats into sugar or 

 glycogen is a question about which at present there is much 

 difference of opinion, and much evidence might be cited on each side. 

 Cremer, however, has furnished apparent proof that glycerin acts 

 as a direct glycogen or sugar-former. When fed, especially in the 

 diabetic condition, it causes an increase in the sugar which can not 

 be explained as a result of protein metabolism. Since in the body 

 neutral fats are normally split into glycerin and fatty acid, the fact 

 that glycerin can be converted to sugar seems to carry with it the 



