THE CYTOLOGICAL CHARACTERS'' ME ARP4S OF 



BY 



M. A. LANE. 



.From .HuH Laboratory of Anatomy, University of Chicago. 

 WITH 1 PLATE. 



In the course of a comparative study of the pancreas, begun in the 

 autumn of 1905, I was struck with a peculiar reaction in certain cells of 

 the Islets of Langerhans in the pancreas of the guinea pig one of the 

 first animals used in the study. This reaction, to be described presently, 

 indicated the existence in the islets of two types of cells, chemically 

 and morphologically different from each other. A part of the ensuing 

 investigation is the subject of the present paper, which is to be followed 

 by a further publication dealing in detail with a comparative study of the 

 islets which I have carried on side by side with that of the islets in the 

 guinea pig. 



The principal difficulty thus far in dealing with the Islets of Langer- 

 hans has been the want of a definite method by which to distinguish the 

 cells of the islets from the cells of the pancreas itself ; for although there 

 is an apparently constant content of islet tissue in the pancreas, and 

 although the areas of islet tissue, in sectioned pancreas, stand out in sharp 

 contrast with the tubules of the pancreas, the physiological distinctness 

 of the one kind of tissue from the other is the very question upon which 

 histologists and pathologists have most disagreed. Pancreas cells ex- 

 hausted by stimulation with alkaloids, and thus thoroughly discharged 

 of their secretion products, have thus far been indistinguishable so far 

 as positive evidence goes from cells of the islets; so that it has been 

 impossible to say that exhausted cells which are indisputably pancreas 

 cells are not essentially the same as islet cells; and, on the other hand, 

 that cells which are indisputably islet cells are not in reality exhausted 

 cells of the pancreas. To establish a method of differentiation between 

 these two orders of cells was a purpose which thrust itself forward very 

 early in the work, as the establishment of such a method would go far 

 toward testing the claims of the two leading theories respecting the 

 meaning of the islets. 



AMERICAN JOURNAL OP ANATOMY. VOL. VII. 

 32 



737105 



