It took forever (it seemed) to track down a photograph of this Civil War supply sergeant-turned medical entrepreneur. One emerged when this letter fell from the insides of a wall being torn out during a home remodel in Battle Creek. It also gives an idea of how he did business AND how he was very, very proud of his signature.
The "Professor" is a title he bestowed upon himself.
There's an article about his life and times, and multiple marriages, at this site: The Kellogg Who Would Be King (shameless self-promotion alert - I wrote it!)