METABOLISM, NUTRITION AND DIETETICS 555 



be separated from the rest of the tissue, the cells of the islets, 

 instead of containing an amylolytic ferment like the alveolar 

 cells, contain a glycolytic ferment, or at least possess tl.e power 

 of destroying sugar. Yet the question of the significance of the 

 islets can hardly be considered settled, and there are good 

 observers who believe that they do not differ essentially from 

 the alveolar tissue, but are formed by certain changes in the 

 arrangement and properties of the alveolar elements. For example, 

 after the gland has become exhausted under the influence of 

 secretion, a great part of the alveoli are said to be converted 

 into islet tissue, which after a period of rest is again altered, 

 so as to yield the characteristic histological picture of the 

 secretory alveoli (Dale). While, then, the importance of the 

 pancreas in carbo-hydrate metabolism is certain, and the 

 dependence of this function upon an internal secretion is highly 

 probable, it is not yet definitely settled whether this secretion 

 is formed in the organ as a whole or only in the islets. That 

 lesions of the pancreas may be concerned in pathological 

 diabetes is well established, and it is of interest in connection 

 with the question we have just been discussing that in a certain 

 number of cases the changes observed have been in the islands 

 (Opie). And in diabetes accompanying cirrhosis of the liver, 

 which has usually been considered to depend upon the hepatic 

 changes, it has been shown that in many, if not all, of the cases 

 the pancreas is also affected by a growth of connective tissue 

 outside the acini (Steinhaus). Some authors, indeed, have gone 

 so far as to say that in all cases of diabetes mellitus there is 

 disease of the pancreas, but of this there is no evidence. 



Ligation, or the establishment of a fistula, of the thoracic 

 duct, causes glycosuria in dogs. It is possible that this is really 

 a mild form of pancreatic diabetes, due to interference with 

 the supply of the internal secretion of the pancreas, or of that 

 part of it which reaches the blood by the lymph-stream (Tuckett). 



Quite recently Pfliiger has brought forward evidence which he 

 considers to show that it is not the removal of the pancreas, as such, 

 but the section of certain nerves running into or through it from 

 the duodenum, which is the cause of the glycosuria. For when these 

 nerves are divided or the duodenum removed while the pancreas 

 remains untouched, the result is the same as if the pancreas itself 

 had been excised. He imagines that these nerves are ' antidiabetic ' 

 that is, in some way oppose the production of sugar while nerves 

 coming from the so-called ' sugar centre ' in the bulb (the centre 

 assumed to be affected in the puncture experiment) favour sugar 

 production. Between these the normal balance is struck in health ; 

 it is the upsetting of this balance by the crippling of the duodenal 

 fibres which is at the bottom of ' pancreatic ' diabetes. It is too 

 early to appraise the value of this conception, especially as the facts 

 upon which it is founded have only been clearly established for 



