M. A. Lane 411 



literature a fact to which Sauerbeck also calls attention. Renaut has 

 been represented as saying that the islets were lymph structures. This 

 is not so. He did not say they were lymphoid tissue a misconception 

 arising from the title of his paper. He simply made a note of their 

 existence, at the same time remarking that they had not been described 

 before. His only reference to lymph tissue in this paragraph of his 

 paper is to the effect that the islets (called by him points folliculaires) 

 were of the size of a lymphatic follicle. 



Other writers hazarded other notions without, however, coming to any 

 satisfactory conclusion. The first definite step in that direction was taken 

 by Lewaschew (11) who, after considerable experiment with mammals, 

 suggested that the islets were temporarily exhausted acini which, after a 

 period of rest, resumed the acinous form. This theory would imply a 

 continuous transformation of acini into islets, together with a dis- 

 appearance of the lumen of the acinus ; and, again, a continuous trans- 

 formation of islets into acini, with an accompanying rebuilding of the 

 lumen, together with the entire complex of changes in the form of the 

 cell, in the nucleus and its content, in the arrangement of the glomerulus 

 of the islet capillary system, and in whatever other changes that might be 

 necessary in this peculiar process. 



Lewaschew's theory further implies that these transformations are 

 continually going on in the entire substance of the pancreas, and he 

 urges, in point of probability that the islet cells are in continuity with the 

 cells of the acini. Eennie (18) has studied peculiar structures in fishes 

 which he identifies with the islets of Langerhans, although these struc- 

 tures lie remote from the pancreas in the abdominal cavity. Generaliza- 

 tions, however, concerning the islets in other animals based upon the 

 existence of these isolated structures in fishes, await the results of Eennie's 

 experimental work. Lewaschew's description of transitional cells, inter- 

 mediate between typical islet and the typical acinus cells is very obscure, 

 and the obscurity is only deepened by the uncolored drawings with which 

 his paper is illustrated. Lewaschew's views, however, have been widely 

 accepted and still have a considerable following. Dale (2) urges them 

 as probable from his experiments on the toad by stimulation with " sec- 

 retin/' although the embryological studies of Helly (6), Opie (15), and 

 Pearce (16) seen to point the other way. 



Laguesse (7) investigated the islets of Langerhans in vipers from 

 the histological point of view, and (8) the islets in the sheep from the 

 histo:enetic point of view. His work, in these respects, has brought to 

 the study of these structures much of the most interesting matter thus 

 far published. Laguesse did not distinguish two types of cells, but he (as 



