I’m looking for a book I read in the late 70’s or early 80’s, about a boy who was deep in the woods with a man, maybe a relative, for an extended period of time. It may be a Canadian book. The man develops appendicitis, and instructs the boy how to cut out his appendix, to save his life. The boy does it, and it works. The boy must be at least 10 years old, he may have been a young teen, I’m not sure.