John James Rickard Macleod (1876-1935) was a Scottish physician and physiologist. Macleod's main work was on carbohydrate metabolism and his efforts with Frederick Banting and Charles Best in the discovery of insulin used to treat diabetes. For this Banting and Macleod were jointly awarded the Nobel Prize for Medicine in 1923. Macleod was awarded half of the Nobel Prize for the discovery of insulin, even though many people (including Banting) publicly insisted that Macleod's involvement was minimal and Best's work had been essential. However, it was Macleod's research plan and his suggestion to inject intravenous degenerated pancreas into depancreatinized dogs that ultimately led to the successful isolation of insulin. Macleod's receiving the Nobel Prize over Best was controversial at the time. Macleod shared his Nobel award money with his colleague James Collip. He died in 1935 at the age of 58.