I don't think I've ever seen this photo nor does this man resesemble anyone from any photo I've seen. But I'll take a wild guess. He 100% looks like a doctor to me, and again I think it's a post-1865, but still 19th century photo. I can't remember having seen a photo of Dr. Patterson, but this is what I would imagine him to look like?!
(The gentleman looks a bit like Sigmund Freud to me, maybe that's what makes me think of a psychology doc:
)