184 PHYSIOLOGICAL, CHEMISTRY 



impulses are carried to the liver by the splanchnics. Glycosuria 

 produced by "diabetic puncture" is known as "puncture dia- 

 betes." 



A second factor which apparently is connected with the con- 

 trol of liver glycogen is the secretion of the suprarenals, adrena- 

 line. If adrenaline is injected, an increase of blood sugar 

 occurs, which has its source in liver glycogen, since no glycosuria 

 results if the glycogen supply of the liver has been exhausted. 

 It has been suggested that the action of the sugar center in the 

 medulla is by way of the suprarenals. This problem is still in 

 doubt ; it is probable that the sugar center works by direct stimu- 

 lation of the liver cells, but is aided and supplemented by the 

 adrenaline secreted from the suprarenals. 



The pancreas has been shown to play an important part in the 

 utilization of sugar by the body. This is connected with the 

 burning of the sugar as fuel and also with the storage of gly- 

 cogen in the liver. If the pancreas of an animal is removed, 

 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 l( 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 bf certain cells present in the 

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



