SECRETION OF THE DUCTLESS GLANDS. 897 



function is not the pancreatic tissue proper, but that composing the 

 so-called islands of Langerhans. In man these islands are scattered 

 through the pancreas, forming spherical or oval bodies that ma}' 

 reach a diameter of as much as one millimeter. The cells in these 

 bodies are polygonal; their cytoplasm is pale, finely granular, and 

 small in amount. The nuclei possess a thick chromatin network 

 which stains deeply. Each island possesses a rich capillary network 

 that resembles somewhat the glomerulus of the kidney. 



According to Ssbolew,* ligation of the pancreatic duct is followed 

 by a complete atrophy of the pancreatic cells proper, while those 

 of the islands of Langerhans are not affected. Since under these 

 conditions no glycosuria occurs, while removal of the whole organ 

 including the islands is followed by pancreatic diabetes, the obvious 

 conclusion is that the diabetes is due to the loss of the islands. 

 This conclusion is strengthened by reports from the pathological 

 side. A number of observers (Opie, Ssbolew, Herzog, et al.) 

 find that in diabetes mellitus in man the islands may be markedly 

 affected. They show signs of hyaline degeneration or atrophy, or 

 in severe cases may be absent altogether. It should be added that 

 this connection of the islands of Langerhans with the internal 

 secretion of the pancreas is not accepted by all writers. Cases 

 of diabetes are reported in which the islands were apparently not 

 affected, f and several observers } contend that the islands represent 

 stages in the development of the ordinary secreting alveoli of the 

 pancreas. The most complete histological work seems to show 

 clearly that the islets are permanent organs which persist as such in 

 the pancreas, and presumably have, therefore, some specific func- 

 tional importance, but the nature of this function and its relation 

 to that of the acinar cells must be considered at present as open 

 questions. 



Several theories have been advanced to explain the action of 

 the internal secretion of the pancreas. It has been suggested that 

 the secretion contains an enzyme which is necessary in the hydrol- 

 ysis or oxidation of the sugar of the body, and in the absence of 

 this enzyme the sugar accumulates in the blood and is drained off 

 through the kidney. In support of this explanation it is found 

 that the respiratory quotient of the depancreatized dog is low, as 

 would be expected if the sugar escaped oxidation. Apparently 

 something is lacking in the normal process, but as the nature 



* "Virchow's Archiv," 168, 91, 1902; also Romans, "The Journal of Med- 

 ical Research," 30, 49, 1914. 



t See Pratt, "Journal of the American Medical Association," December 17, 

 1910. 



t Dale, "Philosophical Transactions," B, cxcvii., 1904; also Vincent and 

 Thompson, "Journal of Physiology," 1906, xxvii., xxxiv. 



Bensley, "American Journal of Anatomy," 12, 297, 1912. 



57 



