M. A. Lane 419 



SUMMARY AND CONCLUSIONS. 



Eecapitulating the facts above described the following positive state- 

 ments may be made : 



1. In the Islets of Langerhans in the guinea pig's pancreas two types 

 of cells, morphologically and physiologically distinct, are demonstrable. 

 These cells show constant reactions to constant chemical tests. I have 

 called these cells A and ft cells, respectively. 



2. The granular content of the A cell differs chemically from that of 

 the ft cell. 



3. The granular contents of the A cell and of the ft cell, while differing 

 chemically from each other, differ chemically from the granular content 

 of the pancreas cell, and cannot, therefore, be identical with zymogen. 



4. The granular contents of the A and of the ft cell differ chemically 

 from the prozymogen manufactured by the pancreas cell as the antecedent 

 of the zymogen granule of the pancreas cell. 



5. The chemical and morphological differences between the A and the ft 

 cell are correlated ; that is, the relations between the anatomical and 

 physiological characters of both types are found to be constant. 



In drawing conclusions from these facts one is led to the conviction that 

 the Islets of Langerhans are structures which in all probability have the 

 function of producing a twofold substance which, poured into the blood 

 stream, has an important effect upon metabolism. That this dual 

 character of cell in the islet is constant throughout the entire class of 

 mammals, if not throughout the entire phylum of vertebrates, is indicated 

 as probable from the results of the comparative study now in progress, 

 which I hope to make the subject of a future publication. The prospects 

 seem to point to certain peculiar variations in the character of these cells 

 in herbivora and carnivora, and to striking and highly suggestive varia- 

 tions among herbivora themselves. 



While these results do not prove that pancreatic cells do not transform 

 into islet cells, or vice versa, they furnish very strong reasons for holding 

 that under normal conditions the islets are physiologically independent 

 of the rest of the pancreas a conclusion in accord with the observations 

 of De Witt and Flint as to the framework and architecture of these 

 structures, and with those of Opie, Pearce, and Helly as to the early 

 differentiation in' the embryo of the specific cells which are their histo- 

 genetic source. 



It is but rational to conclude from the chemical evidence that the 

 substances produced by the two types of cells of the islets are not to be 

 classified with zymogen. If the cells of the pancreas have the power of 



