On the Relations between the „Islets of Langerhans" etc. 81 



On microscopical examination of the pancreas, the islets of Langer- 

 hans are seen to be veiy numerous and large. Tiiey are irregular or 

 lounded in shape, and for the most part circumscribed in outline, but 

 transitions are fairlj^ common. The islets are characterized by the 

 usual wide capillary network. 



Pancreatic tissue is also to be seen gathered in rings round the 

 branches of the portal vein, and outlining the edge of the liver in 

 some places. 



Some of the masses of cells in the islets have an almost identical 

 size and shape with those of alveoli, showing centro-acinar cells and 

 even occasionally a distinct lumen. When one of these columns is 

 cut transversely the cells have the same radial arrangement as in 

 zymogenous tubules. 



Occasionally a comparatively large islet may be seen, almost 

 entirely surrounded by a connective tissue wall, so as to be encapsuled 

 in all directions except at a narrow neck, where the islet tissue is 

 continuous with the zymogenous tissue and shows a gradual transition 

 of structure. The capsule, however, does not everywhere mark the 

 precise limits of the islet, as small groups of zymogenous cells are 

 found within the capsule. The zymogenous tissue immediately outside 

 the capsule is stained more deeply than the general mass (and this 

 has been noted in various animals by several observers), and the same 

 may sometimes be said of this tissue in the interior of the islet limits. 



It will be seen from the above descriptions, that in fishes, just 

 as in amphibians, reptiles, birds, and possibly mammals ^), there are two 

 distinct kinds of structure in addition to the zymogenous tubules. In 

 teleostean fishes however, the bathychrome tissue is not nearly so con- 

 spicuous as in other groups, and is represented almost entirely by a 

 few scattered cells distributed throughout the parenchyma of the gland. 



III. Effects of Inanition upon the Pancreas. 



Statkewitsch'-) appears to have been the first to notice that during in- 

 anition there is an increase in the islet tissue of the pancreas. He considered 



') See appendix. 



2) Arch. f. exper. Path. Vol. 34, p. 453. 1893. 

 Internationale Monatsschrift f. Anat. u. Phys. XXIV. 



