The man was breathing with mechanical assistance--splayed out underwater unconscious. His breaths rasped. The surgeons same around him, in an antibacterial fluid that contained cellular nutrients and narcotics. The pulled apart his skin, then muscle, then bone, then organs. They were teased apart ans spread wide, slowly, over days, so the intervening tissues could heal and grow.
New tissues were fused in. The surgeons worked meticulous, expert in their craft. They knitted in new bones and muscles and skin, and added supplementary hearts and veins and arteries to accomodate the growing biomass. They added new layers to the liver and kidneys, and expanded the bladder. They cut the skull and pried it apart and attached a second cerebellum. They threaded new lines of nerves like ductwork through the new muscles. They molded the skin and muscle to the new framework with new tendons and ligaments and carefully stitched up the skin.
When the skin was sealed they attached electrodes to various parts of the man's body and exercised the new muscles until they were bulky and strong. Then they drained the fluid, to see if the man could stand on his six feet. He did, unconsciously, and the surgeons were satisfied. Then they woke the man, who promptly went into a fit of twitches. He screamed in pained and lolled is head. With his arms he ripped the breathing tube from his mouth and panted. He scrambled around the inside of the vat, scraping madly against smooth wet walls. He looked at his new body and cried.
He slept and then was tranquilized, and slept deeper. When he awoke, he found himself in a large cage, covered with grass and soil on the bottom, and filled with strange trees. Other people, with six legs and two arms and elongated heads stared back at him from the treetops. Seeing that he was awake, they brachiated down to look at him more closely. They were all entirely naked, save for the head and patches of body hair.
"Don't be afraid," said a woman.
"It's not so bad," said a young man.
"Why?" asked the man.
"Look up at the side of the cage," said the woman, pointing.
The man saw dozens of strange faces with large eyes on the other side of the fencing. Their skin was pearlescent, almost luminescent. They blinked slowly. The man rose, examining the faces. He leapt to the fence, really feeling his new muscles for the first time. He climbed until he was above the row of onlookers. He tried to pull the fencing apart but it was made of a strong polymer. Then he shook the fence and screamed at the top of his lungs. The onlookers didn't run away but instead pointed, and looked with greater interest. More of them came to join those already there.
"It's futile!" shouted the woman. "You're just giving them the impression that we're savages!"
"But I am a savage," said the man. He jumped down and looked the woman in the eye. "I used to eat people."
"What?!" said the woman.
"It's true. No human could catch me, but I guess these things found me at random." He licked his lips and the woman stepped back.
"There's only one of you, and dozens of us," said the young man, stepping to the side of woman.
"Is there night here? Is there darkness?" asked the man, stepping forward. The others did not reply. "I will feed. And I bet that will upset those things out there, and when they come for me, I will feed on them too.
"You're insane," said the woman.
"That's what they all say," said the man laughing. He turned and leapt back onto the fencing, and crawled up to the top of the cage where clung and rested. The rest of the people cowered together and looked back at him.