

STORAGE OF CARBOHYDRATES IN THE BODY 127 



fistula had been made between the portal vein and inferior vena cava, but which 

 were otherwise healthy, from twelve to twenty-four per cent of the sugar eaten 

 was excreted in the urine. At least this quantity therefore is retained by the 

 liver of normal animals (and is converted into glycogen). 



The following carbohydrates at least can serve as a source of glycogen: 

 dextrose, levulose, galactose, milk-sugar, cane-sugar, maltose, the last three after 

 being inverted. In this connection it is noteworthy that the glycogen coming 

 from levulose is also dextrorotatory. Levulose, therefore, is either changed first 

 into dextrose, or it passes directly into a dextrorotatory glycogen; in either case 

 the ketone group of levulose is transformed into an aldehyde group. 



Many authors have found a second source of glycogen in proteids. In fact 

 it has been observed that the quantity of glycogen in the liver increases after 

 feeding meat extracted with boiling water, fibrin or chemically pure proteid 

 substances. Pfliiger on the other hand comes forward with the claim that the 

 quantity of glycogen demonstrated in such experiments is not greater than 

 the maximum which has been observed in fasting animals of the same species. 

 Schondorff found no increase of the glycogen in frogs after feeding them 

 with casein. 



The problem has been attacked also from another side. Under normal 

 circumstances sugar appears in the urine only in mere traces ; the total quan- 

 tity of carbohydrate absorbed from the intestine is therefore either burned 

 in the body, or is stored up after having been transformed into glycogen or 

 into fat. It is only when the percentage of sugar in the blood, due to a rich 

 supply of sugar in the food, exceeds a certain low limit (0.20.3 per cent), 

 that a part of the sugar is eliminated through the kidneys (alimentary glyco- 

 suria). In this respect starch forms an exception to the rule for the carbo- 

 hydrates, which is probably due to its relatively slow rate of digestion, a 

 sudden flooding of the blood with sugar being thereby prevented. But in 

 diabetes mellitus as well as after complete extirpation of the pancreas, or after 

 poisoning with phloridzin, the body loses to a greater or less extent either its 

 power to" burn carbohydrates or its power to store them, and the urine under 

 these circumstances always contains more or less sugar. 



These facts have been made use of in attempting to determine whether or 

 not sugar is formed from proteid. Thus, sugar appears in the urine in these 

 diseased conditions after feeding proteid, and if it can be shown that this 

 sugar actually comes from proteid, we should have proof that under some 

 circumstances at least glycogen can be formed from proteid. For the sugar 

 formed from proteid, as well as any other sugar, could, from what we have 

 seen, be changed into glycogen. 



It is a matter of great moment in these experiments to decide whether 

 more sugar appears in the urine than can be accounted for by the glycogen 

 already deposited in the body at the beginning of the experiment. Pfliiger, 

 who recently has subjected the observations on this subject to a searching 

 criticism, takes the view that no proof has thus far been given for the forma- 

 tion of sugar from proteids. It appears, however, that this is going somewhat 

 too far; for in many of the experiments, to explain the quantity of sugar 

 appearing in the urine as derived from the body glycogen, it would be neces- 

 sary to suppose that the animal at the beginning of the experiment had had 

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