Dr Jekyll, I Presume

Douglas A. Anderson quotes an anecdote about Robert Louis Stevenson at A Shiver in the Archive:

Robert Louis Stevenson told a Washington correspondent that his story of “Dr. Jekyl[l] and Mr. Hyde” had for its foundation an incident related to him by a London doctor who made diseases of the brain a specialty. None of his work was absolute fiction, and most of it had a basis in actual experience. “I do not believe,” he said, “That any man ever evolved a really good story from his inner consciousness, unaided by some personal experience or incident of life.”

This passage was published in The Logansport Daily Reporter in January of 1895, about a month after Stevenson’s death. Anderson cites it as the earliest appearance of the quote. Who was the “London doctor” and what precisely was the incident that inspired the Strange Case of Dr Jekyll and Mr Hyde?