206 PHYSIOLOGICAL CHEMISTRY 



sugar appears in the urine, and the amount of blood sugar rises 

 much above the normal. Very little liver glycogen is stored up. 

 The explanation of these facts occupied a great many years, and 

 many points are still obscure. It was found that if even a small 

 portion of pancreas tissue is grafted under the skin and the 

 blood vessels and nerves of the fragment left intact, extirpation 

 of the remainder of the gland does not cause glycosuria. The 

 action of the pancreas evidently is independent of the pancreatic 

 juice secreted into the intestine. If this transplanted portion of 

 the pancreas subsequently is removed, hyperglycemia (excess 

 sugar in the blood) and glycosuria appear. Only within the 

 last few years has fairly conclusive evidence been obtained that 

 the pancreas produces a substance which is given off into the 

 blood, an " internal secretion," without which the tissues are 

 unable to use glucose. If this substance is lacking, the amount 

 of glucose in the blood increases, and the excess is excreted in 

 the urine. It often has been affirmed that the " Islands of 

 Langerhans, " small groups of certain cells present in the 

 pancreas, are responsible for the production of this important in- 

 ternal secretion. The evidence for this is not conclusive, how- 

 ever, and it is still uncertain where in the gland the substance 

 is formed. 



Still another factor is concerned in the control of glucose 

 utilization in the body, and that is the influence of the kid- 

 neys. It has been stated that the kidneys are "set" to retain a 

 definite percentage of sugar in the blood. The kidneys may be 

 injured by the injection of the drug phloridzin. There is a 

 fall in the level of blood sugar, and sugar appears in the 

 urine for several hours. The amount of sugar in the blood falls 

 below the normal. The mechanism of the process is undecided. 

 Possibly the excretion of glucose is an active process, and not 

 simply the passive action of a dam to keep back a certain amount 

 of sugar. In this case phloridzin might act by stimulating the 

 excretion of sugar by the kidneys. It is of interest in this con- 

 nection that the drug causes marked degeneration of kidney 



