The city boy asked for both. So the farmer said, "Here you go, one cock and one pull-it."
The city boy confused asked him what he meant. The farmer said, "A cock is a male chicken and a pull-it is a female chicken."
The city boy said, "Oh," and went on his way with two chickens one under each arm. A bit further down the road he saw a donkey for sale. He went to the man who was selling it to find out how much it was.
The man said, "The ass is 15 dollars." The city boy replied, "No, I want the donkey outside in your yard."
The man just said, "That's an ass."
The city boy, new to these terms, just said, "Oh." and bought the donkey.
As he was leaving the man yelled out, "Wait, the ass gets a bit stubborn about going over hills, so you have to scratch him behind the ears to get him going again." So the city boy is going back home and the donkey stops dead in its tracks and he can't get it to move. He can't scratch its ear because he would have to drop one of the chickens and it would run away. So the city boy starts to fuss and yell at the donkey. While he is doing this a beautiful women walks up and asks him if he needs help.
The city boy thinks, hey why don't I try to impress this beautiful women by using my new slang terms that I learned today. So the city boy turns to the woman and says, "Yeah, could you hold my cock and pull-it while I scratch my ass?"