384 R. R. BENSLEY 



Accordingly we must conclude that the possibility of the trans- 

 formation of acinus tissue into islet tissue or conversely of islet 

 tissue into acinus tissue has not a single well established fact to 

 support it. 



It must be remembered, however, that our results do not justify 

 us in drawing the conclusion that this transformation is impossible, 

 though they make it appear improbable, for we cannot draw con- 

 clusions concerning the fundamental potencies of the cells from 

 negative results of experiments. The latent potency to form 

 islet cells may be present in the acinus cells notwithstanding our 

 negative results, and at any moment an experiment may be de- 

 vised which will enable us to call forth these latent energies. A 

 case of this sort is afforded by the observations of Cade ('01) 

 and Harvey ('07) on the gastric glands of the dog. They found 

 that after gastroenterostomy the chief cells of the fundus glands 

 near the site of operation underwent a change of function and 

 assumed the appearance, and staining properties of the mucous 

 cells which are normally present only in the neck of the gland. 

 Harvey ('07) found that after a certain period these cells recovered 

 their zymogenic function showing that the change was not a 

 degeneration. Here, then, we have the case of a group of cells 

 preserving intact the power to form mucous cells, though under 

 normal circumstances this power is never expressed. In the same 

 way, it is possible to conceive of an experiment which will call 

 forth the latent potencies of the acinus cells and islet cells, and 

 cause either for a time at least, to assume the characters and func- 

 tions of the other type. 



I am the more willing to admit this possibility, because of the 

 fact that the study of the relation of the system of branching tu- 

 bules, which I have demonstrated, to the new formation of acini 

 and islets, has convinced me that the cells of these tubules as well 

 as the cylindrical cells of the ducts from which they arise, are 

 capable of developing into new islets or new acini by mitotic 

 division and differentiation. These cells thus possess at least 

 three developmental potencies, namely they may form acinus 

 cells, A cells, or B cells. This conclusion is also supported by the 

 observations of Laguesse and Gontier de la Roche on the changes 



