Lecture reviews earlier diabetes research which led to the discovery of insulin and then surveys subsequent research carried out by a variety of researchers to try to establish the way in which insulin acts in the bodies of various animals. Briefly mentions the work of Banting who 'with the aid of C.H. Best, and under my direction, succeeded in 1922 in showing that such extracts reduced hyperglycaemia and glycosuria in diabetic dogs.' Mentions the work of Collip in purifying the extract. Explains that the name for the extract, insulin, had previously been suggested by Sir E. Sharpey Schafer 'who had been one of the first to support the hypothesis of the insular derivation of the antidiabetic hormone.'