AQUEOUS EXTRACTS OF PANCREAS

Abstract

Rapid preparation of insulin for medicinal purposes requires that a means be found of removing it from solution by some method more expeditious than that of drying. The previous study was convincing regarding the necessary conditions for rapid extraction. Avoidance of expense obviously favors an aqueous method, but the task of effecting the necessary concentration for use in human cases even by vacuum distillation is time-consuming. The present study was undertaken with a double purpose: (1) to find an inexpensive method of concentration and (2) to take the preliminary steps toward isolation of the pure substance. It was begun in October, 1922, and has been pursued as opportunity afforded the use of potent preparations not required for more urgent purposes. The results here presented should be regarded as preliminary, but will be found, we think, both reliable and consistent. They have led to the development of the improved method of preparation to be described in a subsequent paper. The preparations used were the purest available by the methods in use up to April of this year. For the most part these methods varied little from that described in the previous paper (Paper II of this series). All these preparations gave the biuret reaction varying from feeble to vivid, and it is quite possible that the precipitation recorded in many instances is in part a reaction with protein as well &s with the insulin itself. Nevertheless, the protein was the least in amount we were able to attain and can scarcely have been the only source of the precipitate, for many of the reagents which failed are well known protein