THE PANCREAS 



401 



chemically; it is suggested that they indicate a twofold secretion (Lane). 

 The granules of the islet cells of both types differ markedly also from 

 those of the acinar cells. The islets are of various sizes, ranging from 

 those with only a few or even a single cell to those with many cells 

 (3 millimeters in diameter). The number of islets also varies greatly in 

 different individuals. Thus De Witt (Jour. Exp. Med., vol. 8, 1906) 

 estimated the amount of islet tissue in three apparently normal subjects 



FIG. 375. PANCREATIC ISLET OF CAT. 

 E, endothelial cell; cap, capillary; be, red blood corpuscle. X 750. 



at 1-25, 1-50 and 1-125 of the total volume of the pancreas. By means 

 of intravitam stains (neutral red and janus green), Bensley succeeded in 

 staining differentially the islets of the guinea pig's pancreas. He 

 counted from 13,000 to 56,000 in different specimens. Clark (Anat. 

 Anz., 43, 3, 1913) employed this method in a study of human pancreases 

 secured shortly after death, and estimates the average number of islets 

 at 12 per milligram. In one male subject of 24 years and 140 pounds 

 weight, he estimated the total number of islets at 1,760,000 ; in another 

 of 29 years and 135 pounds weight, only 662, 166. ,0pie (Johns Hopkins 

 Hosp. Bull., 1900) first observed that the islets were more abundant in 

 the tail and least abundant in the head of the pancreas; this observation 

 is confirmed by both Clark and Bensley. Laguesse (Jour, de Physiol. et 



