374 THE FINAL DECOMPOSITION OF FOODSTUFFS IN THE BODY 



In fact after feeding with alanin lactic acid is observed in the urine, some- 

 times also an increase of the liver glycogen. Whether we have here a direct or 

 an indirect formation of glycogen (cf. page 126) cannot be decided. 



Moreover sugar might be formed from leucin by passing through the stage 

 of tetra-oxyamino-caproic acid (actually demonstrated in the body) to dextrose. 



CH 9 .OH 



CO.OH CH a .OH CH a .OH CH.OH 



CH.NH, a CH.NH, CH.OH CH.OH 



CH, ft CH.OH CH.OH CH.OH 



CH y CH.OH COH CH.OH 



X X CHO 



Leucin Tetra-oxyamino- Saccharinic acid Dextrose 



caproic acid 



It would be possible also for leucin, by breaking down the carbon chain 

 between the /3 and y atoms, to pass into sugar by way of alanin and lactic acid. 1 

 Observations on diabetic patients likewise favor this idea of a production of 

 sugar from leucin ; for by feeding leucin, a distinct increase of the sugar elimi- 

 nation is obtained. 



Finally, a production of sugar from diamino acids by way of oxyamino acids 

 is possible. 



2. THE DECOMPOSITION OF CARBOHYDRATES 



The carbohydrates absorbed from the intestine reach the blood for the most 

 part as dextrose. If the percentage of sugar in the blood by reason of an 

 extra large quantity in the food, exceeds a certain low limit (from 0.2 to 

 0.3 per cent), a part of the sugar is eliminated through the kidneys in the 

 urine (alimentary glycosuria, cf. page 127) ; otherwise the urine contains only 

 traces of sugar. The kind of sugar appearing in the urine under these con- 

 ditions is always the same as that fed in excess. Starch does not produce 

 alimentary glycosuria, probably because a sudden flooding of the blood with 

 sugar is prevented by its relatively slow rate of digestion. 



Sugar which is not immediately oxidized is stored in the body either as 

 fat or as glycogen, and is then drawn upon as required. The greatest part 

 of the glycogen is deposited in the liver, but it is not burned there. It passes 

 in some way into the general circulation and is oxidized in the tissues of 

 the body, especially in the muscles. It is possible that this transportation 

 is accomplished in part by the help of the leucocytes. Another and in all 



1 This possibility is strengthened by the observation of Embden, Salomon and Schmidt 

 that acetone is obtained by perfusion of leucin through a glycogen-free liver. Quite re- 

 cently also Lusk and A. R. Mandel have shown that in phloridzin diabetes sarcolactic 

 acid, injected subcutaneously, can be synthesized into dextrose ; and Almagia and 

 Embden have obtained a production of lactic acid by perfusing blood containing glyco- 

 gen or dextrose through a liver containing no glycogen, as well as by perfusing a blood 

 poor in sugar through a liver rich in glycogen. Lusk has suggested, therefore, that the 

 history in the body of carbohydrates derived from proteid may include the following 

 events : (1) lactic acid, (2) dextrose, (3) glycogen, (4) dextrose, (5) lactic acid. ED. 



