"I'm the Meat, You're the Knife" by Paul Theroux in The New Yorker

Now his skin clung to his skull, a tissuey death's head, yellowish, with dry, split lips. When he drew a breath, his eyes goggled from the effort. He looked weird and weightless on the bed, like a castaway adrift on a raft. Where there had been muscle in his arms, there was now slackened sinew, less like flesh than like old meat.
In the Oct. 7 issue of The New Yorker. A wonderful story; destined to become a classic.