Shortly after the discovery of insulin in extracts of the degenerated pancreas of the dog, Banting and Best1extracted other tissues by the same procedure as that used for the pancreas. Extracts of the liver, spleen, thymus and thyroid glands were prepared. The administration of the extracts of liver and spleen to diabetic dogs produced no appreciable effect on the blood sugar level of the animals. The extracts of thyroid and thymus caused distinct but transient lowerings of the blood sugar. Several of their collaborators have made unsuccessful attempts to prepare insulin from other tissues, such as the spleen and the liver. The increased yields which were obtained from pancreatic tissue in December, 1922, by a modification of the procedure previously used, made it seem advisable to us to reinvestigate this matter. We have been able to prepare active extracts from the submaxillary, thymus and thyroid glands and from