420 Cytology of the Areas of Langerhans 



transforming themselves into the cells of the islets which I consider 

 improbable, that transformation must be regarded as a physiological as 

 well as a morphological one. In the course of an examination of many 

 hundreds of islets in the pancreas of the guinea pig I have been able to 

 find but one example of what might be interpreted as a vestige of a 

 lumen ; and this singular structure seemed to be formed by cells of the A 

 type. 



There is one remaining aspect of the problem to be touched upon 

 before closing. This is the possibility that the A and the (3 types of cell 

 are in reality two different phases of the same cell a notion by no means 

 improbable even in the face of the chemical evidence to the contrary. 

 Professor Bensley, who has examined my preparations with considerable 

 care, has pointed out cells which seem (from the anatomical side) to be 

 intermediate between the two types, especially in certain preparations 

 which, at his suggestion, were treated with Ehrlich's haematoxylin before 

 they were submitted to the neutral gentian bath. But even granting the 

 truth of this observation, the force of the general argument remains. If 

 the A and (3 cells are really phases of one and the same cellular structure, 

 their different chemical characters suggest that they are engaged in the 

 manufacture of two different secretions. If we conceive that the A cell 

 changes into the (3 cell, or vice versa, we must conclude that the change 

 implies the taking on of a different physiological activity. Whether or not 

 these two different secretions have to do with the pancreas itself or, 

 through the pancreas with functions lying, in their special or general 

 effects upon the chemistry of the body, near to or remote from, the 

 pancreas, is a matter to be determined by further research. 



I have to thank Professor Bensley, who was kind enough to direct my 

 researches, for his lively interest in the work, for his invaluable sugges- 

 tions as to technique, for his assistance in the interpretation of difficult 

 nodi that arose as the work developed, and for having made preliminary 

 reports of the work to the Association of American Anatomists. My 

 thanks are also due to Mr. Leonard H. Wilder for the fidelity of the 

 drawings which accompany this paper. 



LITERATURE. 



1. BENSLEY, R. R. The CEsophageal Glands of Urodela. Biological Bulletin, 



Wood's Holl, Vol. II, pp. 87-104, 1906. 



2. DALE, H. H. On the Islets of Langerhans in the Pancreas. Phil. Tr.; 



Lond., CXCVII, Bd., pp. 25-46, 1905. 



3. DEWITT, L. M. Morphology and Physiology of Areas of Langerhans in 



Some Vertebrates. Jour, of Exp. Med., New York, Vol. VIII, pp. 

 193-239, 1906. 



