The Humorous versus the Comic Story?

The humorous story   is told gravely; the teller does his best to conceal the fact that he even dimly   suspects that there is anything funny about it; but the teller of the comic   story tells you beforehand that it is one of the funniest things he has ever   heard, then tells it with eager delight, and is the first person to laugh when   he gets through. (Later Twain says that it is "a pathetic thing to see.")

-Mark Twain a.k.a. Samuel Clemens (1835-1910) in How to Tell a Story 

Twain was describing the verbal telling of the story, but what is the distinction between the humorous and the comic story if they are told in writing rather than in speech? Is there a distinction? Or can one write the humorous story gravely and chuckle  in the written comic story?