In Coleridge's epic poem, "The Rime of the Ancient Mariner," the mariner and his shipmates have been without water for an extended period of time. Their ship is "becalmed," meaning that without a breeze, they must sit on the water, unable to move, and unable to take on new supplies. Of all the things they need, they have no water.
When the mariner sights the sail of another ship, he cannot speak.
Through utter drought all dumb we stood!
I bit my arm, I sucked the blood,
And cried, A sail! A sail!
The only way the mariner can speak at all to draw the crew's attention to the sail on the horizon is to bite himself on the arm and drink some of his own blood.