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variety of form in birds’ tails is due to the arrangement of these 
feathers, which are merely extensions of the outer skin, rather 
than to any difference in the inner framework. 
Birds, as a class, are noted for their «esthetic faculties; they 
have an eye for the beautiful. Hence we find various forms of 
purely ornamental tails, often belonging to the male bird only. 
Such are those of some kinds of humming-birds ; also that of the 
male of the Australian lyre-bird. In the cemmon 
towl, the cock has a specially ornamental tail. But the strangest 
kind of adornment is that practised by the Motmots of South 
America. These birds artificially beautify (as they fancy) their 
own tails, by picking off parts of the feathers with their beaks, 
according to a certain fashion of their own invention. 
In some birds the tail is specially modified for use, not ornament. 
Thus, in Woodpeckers it serves as a prop in climbing trees; the 
end of the quills being stiff and pointed, to catch against the bark. 
The very same thing occurs in the Creepers, which belong to a 
different order, quite separate frcm the Woodpeckers. 
The tails of Mammals are built on the same plan as those of the 
lower Vertebrates; but the bones are mostly simplified; for the 
spinal cord stops short, and the neural arches often extend only a 
short distance down the tail. The skin is generally covered with 
hair. But they differ very much from each other, according to 
the different uses to which they are put. Thus, the Kangaroo has 
a think muscular tail, which supports the animal in an upright 
posture, and helps it in hopping. The African Aard-vark and the 
scaly Pangolins have likewise thick tails, like those of Reptiles. 
In the Otter we see a return to the original function of the tail; 
it is flattened, so as to form a swimming organ. In the Beaver, 
and also in the Whales and Porpoises, it is flattened out in the 
opposite direction, namely, horizontally. 
A common form of tail among land mammals is the long furry 
or bushy kind, which has various uses. In the Cat and Dog it seems 
to serve as an outlet for emotion, and a means of expressing the 
feelings. In some breeds of Sheep the tail has become a mere 
reservoir of fat, like the hump of a camel. Inthe Squirrel it hasa 
singular use, as an overcoat or parasol. The word ‘‘ squirrel ”’ is. 
a diminitive of the Latin sciurus, which comes from the Greek shta,. 
a shadow, and oura, a tail; so the name ‘‘squirrel”” means 
‘little shadow-tail.” The great Ant-eater has an enormous 
development of hair on its tail. 
Another shape of tail is the long and thin, with a tuft at the 
end; seen in the Ox, Donkey, Camel, and Giraffe. This is often 
very useful to drive off the flies. But in some jumping animals, 
as the Jerboas, it acts as a balancing-pole. 
