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. Rennie (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 Rennie’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 
histogenetic 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 
