STUDIES ON THE PANCREAS OF THE GUINEA PIG 383 



In my own preparations of the pancreas of the guinea pig I 

 have found abundant examples of the same sort as represented 

 in these figures of Laguesse but I have invariably in these cases 

 been able to trace the connection of these half acini with the duct 

 in series. The examination of preparations in which the duct 

 cells are stained intra vitam by methylene blue confirms this 

 conclusion, for in such preparations large numbers of acini may 

 be found which are separated from islet cells only by a group of 

 centroacinous cells surrounding a lumen, or half acini bordering 

 a cavity which is bounded on the other side by islet cells. Accord- 

 ingly I am of the opinion that Laguesse has not sufficiently well 

 established the principal feature of this case, namely, the separa- 

 tion of the half acini from the ducts. 



An examination, then, of the facts advanced in support of the 

 statement that transitions exist between islet cells and acinus 

 cells reveals the fact that some of these supposed transitions had 

 their origin in an imperfect conception of the islet cell. This is 

 true of the transitions of Dale, Vincent and Thompson, who 

 identified the islet cells by negative characters and thought that 

 they were not essentially different from duct cells 



The idea that the A cells of the islet are transitions, supported 

 by Tschassonikow and for a time by Laguesse, has to commend it 

 only the fact that A cells are different from B cells and that they 

 sometimes occur on the surface of the islets, though not exclu- 

 sively so. On the other hand they occur equally abundantly 

 in the interstitial islets where there can be no question of their 

 origin from acinus cells. 



The transitions of Mankowsky are shown by careful investiga- 

 tion to be in reality degenerations, and the arguments of Laguesse 

 as far as the pancreas of the adult is concerned are reduced to 

 evidences of continuity of the two tissues which certainly do not 

 carry the implication that the one has been derived from the other. 



Furthermore, a quantitative examination of the normal con- 

 tent of islets in the pancreas of the guinea pig, and of that of 

 guinea pigs which have been subjected to secretin stimulation or 

 inanition, estabhshes the fact that the number of islets is not influ- 

 enced by these conditions. 



