Everybody knows that tails serve a great variety of purposes. To mention a few: The horse and ox use their tail to drive off troublesome insects. Some kinds of apes have long prehensile tails with which they swing themselves from branches or reach distant fruit. The kangaroo's tail forms a kind of extra leg, and is also serviceable in jumping. The beaver is said to beat with its tail the mud of which its house or dam is built, as well as to use the organ in swimming. The tails of fishes act like rudders, and in whales, for example, they are powerful propellers, as also a means of attack or defence. Birds of high flight have their tail feathers adapted as a steering apparatus; while the tails of parrots, toucans, and climbers generally, incline downwards, and aid in laying hold of trees. The tail in some reptiles is important for locomotion. Scorpions have in their tail a formidable weapon; and the noise made by the rattlesnake when roused is given from its tail.

There is a good deal of expression in tails. A cat when unexcited has her tail bent towards the ground and quiet; but when the animal is under lively emotion, the tail shews movements which are not of chance character, but predetermined by nature—such and such an emotion causing such and such a movement. When the cat feels afraid when seized, for example by the neck, the tail goes down between her legs. On sight of an agreeable morsel of meat, the tail is raised straight up. When angry, the cat bends her tail into two curves of opposite direction—the greater curve at the base, the lesser at the extremity—while the fur is erect throughout. When on the alert for prey, she lashes her tail from side to side. On the other hand, the dog wags his tail to testify joy; while (as with the cat) fear sends it down between his legs. We are all familiar, again, with the comical appearance of a herd of cattle, driven to despair by insects, rushing about a field on a hot day with their tufted tails erect as posts. Dr John Brown, in one of his racy sketches, tells of a dog of his whose tail had rather a peculiar kind of expressiveness. This tail of Toby's was 'a tail per se; it was of immense girth, and not short, equal throughout like a policeman's baton; the machinery for working it was of great power, and acted in a way, as far as I have been able to discover, quite original. We called it his ruler. When he wished to get into the house, he first whined gently, then growled, then gave a sharp bark, and then came a resounding mighty stroke, which shook the house. This, after much study and watching, we found was done by his bringing the entire length of his solid tail flat upon the door with a sudden and vigorous stroke. It was quite a tour de force or a coup de queue, and he was perfect in it at once, his first bang authoritative having been as masterly and telling as his last.'

There seems to be good reason for believing that rats sometimes use their tails for feeding purposes where the food to be eaten is contained in vessels too narrow to admit the entire body of the animal. A rat will push down his tail into the tall-shaped bottle of preserves, and lick it after he has pulled it out. A gentleman put two such jars of preserves covered with a bladder, in a place frequented by rats; and afterwards found the jelly reduced in each to the same extent, and a small aperture gnawed in the bladder just sufficient to admit the tail. Another experiment was more decisive. Having refilled the jars to about half an inch above the level left by the rats, he put some moist paper over the jelly and let it stand in a place where there were no rats or mice, till the paper got covered by mould. Then he covered the jars with a bladder and put them where the rats were numerous; as before, next morning the bladder had again been eaten through, and on the mould there were numerous distinct tracings of rats' tails, evidently caused by the animals sweeping these appendages about, in the fruitless endeavour to find a hole in the circle of paper which covered the jelly.

An example of the practice of vivisection (which is happily less common in this country than on the continent) is presented in an experiment made lately by an eminent French physiologist with the tail of a young rat. Readers are doubtless aware of the curious results that may be obtained by skin-grafting. The experimenter referred to skinned a little portion of the tip of the rat's tail, made an incision in the back of the animal, inserted the skinned tip in this hole, and fixed it there. In course of time the wound healed, and the animal went about with its tail thus transformed into something like the handle of a teapot. After eight months the savant cut the handle in two; then on pinching the end of the part left in the back, the rat appeared to feel pain, and tried to escape. It was thus shewn that the sensitive nerves in the end of the tail had formed a true connection with the nerves in the back issuing from the spinal cord; and that they conveyed an excitation in an opposite direction to that in which they convey it normally.

The trick which came under the notice of the French correctional police will perhaps here recur to recollection. A person complained that he had been imposed upon by the purchase of an animal represented to be 'an elephant rat;' that is, a rat with a trunk and tusks resembling those of an elephant. The trunk was nothing more than part of a rat's tail stuck into the snout of the animal, where it grew as if natural. As for the tusks, they were two of the teeth in the upper jaw which had been suffered to grow by removing the two corresponding teeth in the lower jaw against which they used to grind and be kept short. More ingenious than honest, the fraud was duly punished.

Crocodiles have enormous tails; of sixty vertebrÆ there are more than forty which are caudal. The organ is rather cumbrous to them on land, and this fact affords an opportunity of escaping from them by making quick turns, which they do not readily follow. But their powerful tail must be of immense value to them in swimming.

There is strong probability that the tail of some animals covered with fur serves the purpose of a protection to the air-passages of mouth and nose during sleep, as also the retention of heat. This will be apparent to any one who observes the position into which the tail is curled in such cases, and the face brought into contact with it.

Frogs have no proper tails, but in the tadpole stage they have, and their locomotion by means of them is familiar to everybody. A similar mode of locomotion is observable in the minute animals termed Flagellata, which advance by lashing their tails from side to side. The motions of several of those microscopic organisms known as Bacteria, found in putrefying infusions of organic matter, are at present somewhat enigmatical. But they are to a certain extent explained by an interesting observation made lately by MM. Colin and Warming. With sufficient magnifying power these naturalists have found tails in several of the Bacteria. They vary in number from one to three, are situated at one end of the axis of length, and capable of rapid motion; by which the movements of these minute creatures may fairly be accounted for.

The last thing we have to say on the subject is to express our gratification at the change which has taken place in treating the tails of horses. The odious and cruel practice of, docking them, once so prevalent, has been happily abandoned, and the horse's tail is now left to attain its natural graceful dimensions.