CYTOLOGICAL STUDIES OF LANGERHANS's ISLETS 39 



of which is extremely difficult to determine. From the topo- 

 graphical and cytological behavior of the islet, it is impossible to 

 conceive that it has no function, or that there exists any connecJ:ion 

 between the islet and the nervous or lymphatic system. The pro- 

 toplasm of the cell elements composing the islet is too well differ- 

 entiated to be regarded as embryonic remains. In their fully 

 developed condition they have no connection with the lumen, 

 which excludes the possibility that they participate in the pan- 

 creatic secretion. The islet cells show no sign of regressive meta- 

 morphosis. There can be found no degenerative change of the 

 nucleus; the latter rather multiplies by mitosis and, in part at 

 least, by amitosis which never leads to the death of the cell. 

 Most of the islet cells contain fatlike corpuscles; this accumulation 

 of fat, however, is not associated in any way with the degeneration 

 of the cell as mentioned by Dogiel, but seems rather to have an 

 important share in the function of the cell. Finally, islet cells 

 cannot be identified with a resting stage of acinus cells, for they 

 differ from the exhausted cells in their cytoplasmic structure. 



The various views mentioned above being excluded as im- 

 probable, we are left with a conception that the islet is an organ 

 for internal secretion, giving certain substances to the blood- 

 stream. I, for my part, do not hesitate to admit this hypothesis 

 as the most probable one. A strong argument for it is that most 

 of the islet cells are, at one or both ends, in contact with dis- 

 tended capillaries. Even when there is a solitary cell or a few 

 cells forming a group, the blood-capillary to which the islet cells 

 are attached has a wide lumen. It is also seen that the blood- 

 capillary widens with the development of the islet. These facts, 

 together with the fact that the islets have no lumina which are 

 continuous with the pancreatic duct, strongly suggest that the 

 cells bear a close relation to the blood-vessels. Import and ex- 

 port of substances are faculties with which living cells are en- 

 dowed; the gland cells, for example, take on materials from the 

 blood-stream in order to give the secreted fluid to the secretory 

 duct. In such a tissue as the islet, where most of the cells are 

 not in contact with any other tissue than a, blood-vessel, the 

 elaborated products can be given only to the blood-stream. 



