How does Christopher Marlowe use imagery in The Jew of Malta?

Marlowe uses the image of Barabas' nose in mulitiple ways.... as a symbol, a souce of humor, and a source of denigration.

Oh brave, master, I worship your nose for this."

"I have the bravest, gravest, secret, subtle, bottle-nosed knave to my master, that ever a gentleman had."

"God-a-mercy nose"