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TAIL
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A tail is the section at the rear end of an animal's body, the term particularly referring to such a section which forms a distinct, flexible appendage to the torso. It is the part of the body that roughly corresponds to the sacrum and coccyx in mammals and birds. Tails are mostly a feature of vertebrates, however some invertebrates have tail-like appendages, such as the tail of the scorpion, or the furcula of the springtail.
Function
Tails perform various different functions in animals, they are used by fish and other marine life for locomotion, while some land animals use them for balance (e.g. cats) or even for grasping (e.g. monkeys).
Tails can also be useful as for social signals, as used by deer to warn of possible danger, or by domestic dogs to indicate emotions. Different evolutionary pressures have led to armoured tails, some containing venom, as in the case of scorpions.
In some species of lizard, the tail is able to be permanently detached ("cast") from the body if necessary, with the intent of escaping a grip or distracting a predator long enough to allow the lizard to escape. Usually their tails will grow back over time, though generally darker in colour than the original.
In most birds, tails consist of feathers of extended length, the function of which is to act as a rudder to balance and steer the bird in flight, also to provide balance when perched.
Human tails
Human embryos have a tail that measures about one-sixth of the size of the embryo itself. As the embryo develops into a fetus, the tail is absorbed by the growing body. Infrequently, a child is born with a "soft tail", which contains no vertebrae, but only blood vessels, muscles, and nerves. Modern procedures allow doctors to eliminate the tail at delivery. The longest human tail on record belonged to a twelve-year-old boy living in what was then French Indochina, which measured nine inches (229 mm).[1]
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