906 



PHYSIOLOGY 



is the protein of the tissues. The nitrogen excreted in the urine rises 

 in amount in proportion to the quantity of sugar excreted, and there 

 is a constant ratio between the amount of nitrogen and the amount 

 of sugar excreted in the urine. In some experiments this ratio D : N 

 has been 2'8 : 1. If meat be administered to such starving animals 

 with glycosuria, the D : N ration does not alter ; the amount of 

 nitrogen in the urine increases, but the sugar increases in the same 

 proportion. The sugar production is therefore proportional to the 

 protein metabolism and must be derived from protein. The source 

 of the sugar is the amino-acids of which the protein is composed. In 

 one experiment in which pancreatic digest of meat was given to a 

 phloridzinised dog, 2'4 grm. of glucose were excreted for each 

 gramme of nitrogen. In the same way, glycine, alanine, and asparagine 

 increase the glucose output in such an animal. We must assume that 

 the amino-acids produced in digestion or by the autolysis of the 

 tissues undergo deamination and that the sugar is formed by a process 

 of synthesis from the oxyacids thereby produced. On the other hand, 

 the administration of fat to phloridzinised dogs gives no increase in 

 the output of sugar. The drain of sugar from the organism determined 

 by the action of phloridzin on the kidneys thus necessitates a continued 

 breakdown of the nitrogenous tissues of the body in the effort to 

 maintain a normal supply of sugar to the tissues, and unless excessive 

 feeding be employed the animal must waste. The great increase in 

 the nitrogenous output resulting from the condition of phloridzin 

 diabetes is shown in the following Table (Lusk) : 



The constant drain of sugar will in time involve a relative carbo- 

 hydrate starvation of the tissues, which will make good their energy 



* The high D : N ratio on the first day is evidently due to the conversion 

 of the glycogen still present in the body. 



