Prescription

A woman walks into a pharmacy and asks the pharmacist, "I'd like to buy some arsenic, please."

"Arsenic?! What in the world for?"

"I want to poison my husband," she replies. 

"Lady, you can't just walk in here and ask for arsenic to kill your husband!"

"Well, I recently caught him cheating on me." And she proceeded to take a large picture from her purse showing her husband in the throws of passion with the pharmacist's wife.

He exclaims, "Well, now, you didn't say you had a prescription!"