The "Canadian Connection" portion of Lincoln North: a virtual exhibit at McGill University in Montreal, Canada included a most interesting story about Louis (Lewis) Joseph Archibald McMillan, from the book "Lincoln frees the slaves," by Stephen Leacock.
"McMillan...was the surgeon aboard the ship Peruvian bound for Liverpool, which numbered among the passengers John Surratt, travelling under the name, McCarty. It was this same McMillan who reported Surratt once his identity had become manifest and landfall reached, eventually leading to John Surratt’s arrest."
Lewis McMillan was a McGill University graduate.
One of the many references to Dr. McMillan from the Trial of John H. Surratt in the Criminal court for the District of ..., Volume 2: