How was John James Rickard Macleod awarded the Noble Prize in Physiology or Medicine?

Name: John James Rickard Macleod.
Country: Scotland, United Kingdom.
Date of Birth: 6 September 1876.
Died: 16 March 1935.
Education: University of Aberdeen.
Subjects Of Study: Carbohydrate insulin.
Known as: Co-discovery of insulin.
Noble Prize Year: Nobel Prize for Peace in 1923, for his discoverers of insulin.