THE METABOLISM OF THE CARBOHYDRATES 319 



Langstein suggests that, besides albamin, globulin may contain some 

 N-free polyose yielding on hydrolysis dextrose ; or it may be that 

 the dextrose is adherent as such to the albamin molecule. It 

 should be pointed out, however, that only 2 per cent, of sugar has, 

 so far, been detected in globulin. Simon has recently described 

 in the liver an albumose which contains sugar. 



There is too little matter on hand to enable us to say how the 

 carbohydrate group is attached to the proteid molecule. By the 

 action of acids on proteid, the product which remains behind after 

 the carbohydrate group has been split off, although it gives the biuret 

 reaction and is precipitable by alcohol, is more probably of the nature 

 of a proteose or peptone than native proteid. 



After we have studied the nature and mechanism of phloridzin 

 diabetes, we shall see that there is reason to believe that a loose 

 chemical compound of a colloidal nature exists between serum 

 globulin and dextrose (see p. 363). 



Soon after absorption into the blood, therefore, the sugar 

 in great part becomes converted into glycogen, and possibly also 

 into proteid. The biological evidence of this latter transformation 

 we will consider later; for the present, a careful study of the 

 derivation and fate of glycogen in the organism will occupy 

 our attention. 



Although, as we have already seen, the liver is not the only 

 organ in which glycogen is found, it is evident that a careful 

 study of the so-called glycogenic function of the liver must be 

 of very great importance, and for many reasons : the percentage 

 of glycogen is much higher in this than in any other organ or 

 tissue; the anatomical position of the organ, and the fact that 

 the percentage of sugar in the systemic blood is nearly constant 

 whereas that of the portal blood varies according to the activity of 

 digestion, suggest the glycogenic function of the liver as the one 

 which mainly regulates the supply of sugar in the systemic blood ; 

 moreover, under certain conditions, we can approximately calcu- 

 late, from the amount found in this organ, how much glycogen 

 there is in the entire body. 1 



1 It should, however, be noted that different workers do not agree on the 

 quantitative relationship between the hepatic glycogen and that deposited else- 

 where in the body. Ott, for example, states that there is an equal amount in 

 the liver and in the other tissues, whereas Salkowski and Frentzel found more 

 in the liver. Kiilz found in starved hens a large excess in the body compared 

 with the liver. 



