III. On the "islets of Langerhans" in the pancreas

Abstract

The observations here described are the outcome of an investigation of the histological changes produced in the pancreas by the activity called forth by “secretin” (Bayliss and Starling (1)). In all former investigations of these changes the secretion of the gland has been provoked by the natural stimulus of digestion or by the administration of pilocarpine. The former is at best a slow stimulus, and the histological variations at different periods of normal digestion slight; the latter was found in practice much inferior to secretin as a pancreatic stimulant, judging by the volume of juice secreted. It seemed worth while, therefore, to repeat the former histological observations with the use of secretin, which, besides being a far more powerful stimulant than pilocarpine, has the advantage that its action is an intensification of the normal physiological stimulus. It may be said at once that, in regard to the cytological details of the changes involved in the actual secretion—the discharge of the zymogen granules and the growth from the base of the cell of the chromatophilous substance—nothing new was observed. The changes were in many cases more complete, but of the same kind as those described as a result of the action of pilocarpine. My attention, however, was early drawn to very obvious differences produced in the structures called "islets of Langerhans,” “intertubular cell-clumps,” &c. These changes form the main subject of this paper, and a short historical account seems called for of the views which have been held as to the nature and function of these structures, which will be here referred to as “islets of Langerhans” or “islets.”