Who is Dr. Stewart Rawlings Mott from Slapstick: Or, Lonesome No More! and what is their importance?

Dr. Stewart Rawlings Mott was Wilbur and Eliza's childhood pediatrician. He checks on them daily, and the children nickname him Flocka Butt. Wilbur always wondered if Mott ever suspected their intelligence. He is described as melancholic.