Posted by DaveIt's not exactly a Human Centipede, but it's certainly reminiscent - and perhaps just as unlikely. From Francis T. Buckland's Curiosities of Natural History (1856), quoting a case presented in an unnamed French newspaper:
"The trumpet rat, he tells me, is not a supernatural thing, it is an invention due to the leisure moments of the Zouaves. This is how they make them: you take two rats; you tie their paws firmly on a board, the nose of one close to the end of the tail of the other; with a pen-knife or a lancet you make an incision into the nose of the rat which is hindermost, and you graft the tail of the first onto the nose; you tie firmly the muzzle to the tail, and you leave the two rats in this position for forty-eight hours.
At the end of the time the union has taken place, and the two parts are grown together; then you cut off the tail of the rat which is in front to the required length, and let him go, but still keep the other tied to the board but with his head loose, and you give him something to eat. At the end of a month or more the wound is perfectly healed, and the eyes of the most curious scrutators would not see a hint of the grafting."
It's worth noting that the above excerpt doesn't even scratch the surface of this deliriously rambling, almost relentlessly bizarre book - expect to see a lot more from Mr. Buckland's masterpiece in the coming months.