Photocopy of the carbon copy of a typescript letter. Gives Macleod's account of the discovery and development of insulin with an explanation of the role he played. Includes Macleod's letter to Col. Albert Gooderham, dated Sept. 20, 1922, a note added to the original account, dated May 1923, and an appendix. This document was written in response to Col. Albert Gooderham's request that Banting, Best, and Macleod each write accounts of the discovery of insulin, detailing their particular contributions and those of Collip.