The Craziest Animal Experiments

Rather than being useful in itself, the experiment was simply an exercise in gene manipulation quite literally, a flashy stunt that could lead the way to more practical gene therapies. This is but the latest example in a long history of wacky, and sometimes ethically controversial, animal experiments, some of which have led to invaluable medical applications for humans. Here are a few of our favorite feats in the history of Frankenstein-esque science.

In the 1950s, a Soviet scientist named Vladimir Demikhov pioneered the field of organ transplantation using dogs. In one infamous experiment, he fashioned a "multi-dog" surely one of the most mind-boggling creatures ever created by man.

According to a 1955 article in Time Magazine, Demikhov "removed most of the body of a small puppy and grafted the head and forelegs to the neck of an adult dog. The big dog's heart ... pumped blood enough for both heads. When the multiple dog regained consciousness after the operation, the puppy's head woke up and yawned. The big head gave it a puzzled look and tried at first to shake it off."

Remarkably, both dogs kept their own personalities, post-surgery. "Though handicapped by having almost no body of its own, [the puppy] was as playful as any other puppy. It growled and snarled with mock fierceness or licked the hand that caressed it. The host-dog was bored by all this, but soon became reconciled to the unaccountable puppy that had sprouted out of its neck. When it got thirsty, the puppy got thirsty and lapped milk eagerly. When the laboratory grew hot, both host-dog and puppy put out their tongues and panted to cool off." [Read: How Did Dogs Get to Be Dogs? ]

Unfortunately, the experiment wasn't a total success: "After six days of life together, both heads and the common body died."

In a slideshow of freakish animals, who could forget little earmouse. The "ear" emerging from this lab rodent's back heard nothing: It was actually just an ear-shaped tissue structure grown by seeding human cartilage cells into a biodegradable mold. The Vacanti mouse, as it's more formally known, was endowed with its ear by Dr. Charles Vacanti, a transplant surgeon, and his colleagues at Massachusetts General Hospital. They performed the stunt in 1995 to demonstrate a potential method of cartilage transplantation into human patients.

Not all strange animal experiments result in hideous monstrosities. Take ligers, for example the magnificent offspring of male lions and female tigers that take an inter-species shine to one another when their paths cross in captivity. At more than 900 pounds and 12 feet long, ligers are the largest cats on Earth, weighing almost 100 times more than house cats and almost twice as much as either Panthera tigris or Panthera leo. [Read: Why Don't Tigers Live In Africa? ]

Aside from spurring inexplicably gargantuan growth, "hybrid vigor" also makes these beasts healthier and sometimes longer-living than their parents. Adding to the genetic mystery of why ligers grow so large, tigons hybrids born to male tigers and female lions exhibit no such anomaly; they're just tiger-sized.

In 2010, neurobiologists at the University of Pittsburgh taught a monkey to control an advanced robotic arm with its mind. They gave the monkey two brain implants, one each in the hand and arm areas of its motor cortex. These monitored the firing of motor neurons and sent the information to a computer, which translated the patterns into commands for the robotic arm. As a result, the monkey was able to manipulate the arm, which had no less than seven degrees of freedom, with its thoughts alone. It learned to use it to reach for food pellets, press buttons and twist knobs. [Read: What's It Like to Be a Monkey? ]

The scientists weren't just monkeying around: Their work could lead to brain-machine interfaces that will allow paralyzed people to operate advanced prosthetics with their minds just as the rest of us move our fleshier limbs.