Clinical professors? (Humanities)

[lorena25]

I am applying for a PhD in the humanities and have been checking out the "people" sections at some universities, to see if any professors might fit as potential advisors. I've discovered that besides Professors (Regular, Associate, Assistant), there are also Clinical Professors (Associate, Assistant). I'd appreciate it if someone could explain to me just what the Clinical Professor rank means. It seems that some of the Clinical Professors correspond highly with my own interests, but would it be a mistake to mention them in the Statement of Purpose as potential advisors?

Thanks!