554 A MANUAL OF PHYSIOLOGY 



Removal of the fragment of pancreas is followed by the whole 

 train of symptoms associated with total extirpation of the 

 organ. 



Although as yet we are ignorant of the precise manner in 

 which the pancreas influences the metabolism of the body, it is 

 impossible to doubt, in view of the facts we have mentioned, 

 that, like the liver, in addition to carrying on the exchanges 

 necessary for the preparation of the ordinary or external secre- 

 tion, the gland has other important relations with the circu- 

 lating fluids, giving to them or taking from them substances 

 on the manufacture or destruction of which the normal metabolic 

 processes depend. It has been suggested that the pancreas 

 neutralizes or renders harmless some toxic substance formed 

 elsewhere in the body, the action of which produces glycosuria. 

 But no evidence of the existence of any such substance has been 

 obtained, and the transfusion into a normal dog of blood from 

 a depancreatized animal, which ought to be laden with the 

 hypothetical toxic material, does not cause glycosuria. It is 

 much more probable that the hyperglycaemia on which the 

 glycosuria depends is caused by the absence of something 

 normally produced by the pancreas, and which is indispensable for 

 the due regulation of the sugar-content of the blood. This some- 

 thing, as already pointed out in discussing pathological diabetes, 

 may either be necessary to regulate the transformation of 

 sugar into glycogen, so that too great a surplus of sugar does 

 not remain unchanged, or to regulate the transformation of 

 glycogen into dextrose and prevent too hasty and too extensive 

 action by the glycogenase, or, finally, to regulate and to aid in the 

 normal combustion of the sugar in the organs (p. 517). The seat 

 of the internal secretion of the pancreas seems to be the very 

 vascular epithelioid tissue which is peculiar to this gland, and 

 occurs in islands between the alveoli (islands or islets of Langer- 

 hans) (Schafer) . For animals survive the complete atrophy of the 

 ordinary secreting epithelium caused by the injection of paraffin 

 into the ducts, and no sugar appears in the urine. The islets 

 remain intact. When a portion of the pancreas is separated 

 from the rest, and its duct ligated, it undergoes extensive atrophy, 

 a tissue remaining which is apparently composed of enlarged 

 islands of Langerhans and remains of pancreatic ducts. If the 

 rest of the gland is now removed, no glycosuria occurs, even when 

 considerable quantities of dextrose are injected. But when the 

 atrophied remnant is also removed, typical pancreatic glycosuria 

 at once ensues (W. G. MacCallum). 



As further evidence that the islets have a different function 

 from the pancreatic alveoli may be cited the statement that in 

 teleostean fishes, in which the islands are so large that they can 



