CYTOLOGICAL STUDIES OF LANGERHANS'S ISLETS 29 



tophile granules, and which are scattered through the pancreas 

 individually or in small groups, as transitional between the 

 acinus and islet cells. 



Other investigators have opposed the above view, and they 

 attach considerable importance to the presence of the connective- 

 tissue membrane which forms a sort of capsule around the islet, 

 sharply marking it off from the acinus tissue. Piazza, who takes 

 into consideration the fact that the behavior of the blood and 

 nerve supply and of the connective tissue of the islet is quite dif- 

 ferent from that of the acinus tissue, and especially the fact that 

 the chemical characters of cells of the two tissues differ widely 

 from each other, has come to the conclusion that a transition 

 between the two is impossible. 



Experimental studies also have been made to solve this com- 

 plex and difficult problem. Some investigators have found that 

 the ligature of the pancreatic duct results in the disappearance 

 of the acinus tissue, while the islets remain intact. Schulze 

 ('00), Ssobolew ('02), and others have, from these observations, 

 been led to the conclusion that the islet is an independent organ, 

 whereas Laguesse ('05) claims that these findings are not contrary 

 to his view that the islet is derived from the acinus tissue. Man- 

 kowski found that both tissues disappeared in the same experi- 

 ment. On the other hand, there are many investigators who 

 have observed, after the injection of pilocarpin or secretin or 

 after a period of fasting, that the islets increased in number; ac- 

 cording to Gelle ('11), Fischer ('12), and Retterer and Lelievre 

 ('13), this is due to the increased transformation of acinus cells 

 into islet ceUs. 



Kyrle and Weichselbaum (Kyrle, '08; Weichselbaum and 

 Kyrle, '09) believe that the islet cells are derived from small 

 pancreatic ducts, while Hansemann ('02) attributes a mesen- 

 chymal origin to the islet. Their views, however, seem to have 

 gained few adherents among histologists. 



The behavior of the capsule or the size and number of the islets, 

 in either normal or experimental conditions, is not sufficient to 

 solve the problem of the genetic connection between the islet 

 and acinus tissue. Transparent cells containing no zymogen 



