46 INTERNAL SECRETION 



Experiments involving ligature of the pancreatic duct 

 have given contradictory results in the hands of various 

 observers. Many writers have alleged that if a portion of 

 the pancreas is separated from the rest of the gland and its 

 duct tied it atrophies and leaves a tissue containing enlarged 

 islets. 



Schafer was the first to suggest that the islets of Langer- 

 hans are the part of the pancreatic tissue concerned with 

 carbohydrate metabolism. A number of more recent observers 

 have found in cases of diabetes mellitus that the islets are 

 affected by a hyaline degeneration, atrophy, or inflammatory 

 changes ; but others have been unable to confirm these results. 

 Notwithstanding the conflicting nature of the evidence upon 

 this point, a large number of pathologists have at any rate, 

 until quite recently appeared to favour the view that the 

 islets of Langerhans constitute a tissue &ui generis, whose 

 function it is to control, by means of some kind of internal 

 secretion, the metabolism of sugar in the body. 



Diamare has, indeed, put forward some experimental work 

 in support of this definite view as to the function of the islets. 

 He finds that the amylolytic ferment occurs only in the ordinary 

 pancreatic cells, while it is absent in the islets of Langerhans. 

 He states that the islets possess the power of inverting grape- 

 sugar, and is of opinion that these structures are intimately 

 concerned in the economy of glucose in the body. The 

 glycolytic action of the islets in vitro is very weak, and he 

 looks upon the tissue as furnishing an endocrine zymoplastic 

 secretion. Hyperglycaemia and diabetes are in this view the 

 result of functional insufficiency of the islets. This observer 

 further records certain modifications occurring in the islets 

 of Motelkt tricirrata as the result of the injection of glucose 

 into the abdominal vein. 



As we have seen, the present writer was the first to prove 

 experimentally that the islets of Langerhans actually pass 

 through a structural cycle, corresponding to a cycle of changes 

 in physiological conditions. We were able to provoke ex- 

 perimentally the formation of new islets at the expense of the 

 exocrine parenchyma, and then to induce their disappear- 

 ance by a new transformation into acini. 



Laguesse, working with the pigeon, has been able to confirm 

 our results. He has performed a very large number of expert 



