648 DIABETES 



of injection. Once established, the glycosuria then tends to proceed at 

 a uniform rate as long as the rate of injection and other conditions re- 

 main fixed. However, if the injection rate is again reduced to 0.8 gm. 

 per kg., glycosuria promptl}^ ceases. Thus during the continuance of 

 an injection at the latter (0.8 gm.) rate there can be no continued 

 accumulation of unchanged glucose in the body, but the rate of injec- 

 tion is equalled by the rate of utilization if we leave out of considera- 

 tion the trace of sugar which can be detected in the urine by refined 

 methods. It is important to note that it makes no appreciable differ- 

 ence whether one uses an 18 or a 72 per cent, glucose solution for in- 

 jection. The tolerance limit for glucose may be demonstrated at the 

 same point regardless of wide variation in the quantity of water ad- 

 ministered with the glucose, even though the blood volume and the 

 blood sugar percentages may be influenced by variation of the water 

 supply. Also, if glucose is injected continuously and uniformly at a 

 rate productive of some glycosuria, the glucose excretion may proceed 

 at a constant rate in spite of marked variation in the water supply 

 during successive hours. A certain dog receiving by vein 20 gm. of 

 glucose per 10 kg. per hour for 8 hours, excreted every hour close to 

 0.42 gm. of sugar per 10 kg. of body weight. Yet during the ex- 

 periment water was injected at varying rates into the same vein with 

 the glucose, so that the hourly volume of urine varied between 6 c.c. 

 and 128 c.c. and the percentages of sugar in the urine varied between 

 0.35 and 4.9. This emphasizes the fundamental importance of the 

 rate at which sugar is supplied to the organism in determining the 

 occurrence or non-occurrence of glycosuria and in fixing the rate of 

 excretion when the latter occurs. 



In view of the above generalities several specific mechanisms sug- 

 gest themselves by which glycosuria might be produced : 



(1) An increased supply of preformed glucose to the whole organ- 

 ism from without (alimentary glycosuria). 



(2) A decreased utilization in the organism as a whole (pancreatic 

 diabetes) . 



(3) An increased supply to the kidneys resulting from the hbera- 

 tion into the blood of sugar previously stored or combined in other 

 organs. Thus, the rapid hydrolysis of glycogen following puncture 

 of the floor of the fourth ventricle and analogous nerve stimulations, 

 and occurring in the acid, asphyxial, narcotic, thja-oid, epinephrine, 

 and hypophysis glycosurias. In an analogous manner lactose may 

 enter the circulating blood from the mammary gland, and pentose 

 from unknown sources. 



(4) An increased supply to the kidneys due to decreased utilization 

 in other organs. The breaking down of glycogen mentioned in (3) 

 might be so interpreted and one might think of the possibility that in 

 various diseases the ability of a part to utilize sugar maj'^ be altered. 



(5) Decreased utilization in tlu^ kidney itself. 



