the life of
the bird. There are, of course, many exceptions to such a generalisation
as this. For instance, many species of sparrows are dull-coloured. We must
remember that the voice--the calls and songs of birds--is developed to a
high degree, and in many instances renders bright colouring needless in
attracting a mate or in locating a young bird.

As we have seen, the sense of smell is very highly developed among
four-footed animals, but to make this efficient there must be something
for it to act upon; and in this connection we find some interesting facts
of which, outside of scientific books, little has been written. On the
entire body, birds have only one gland--the oil gland above the base of
the tail, which supplies an unctuous dressing for the feathers. Birds,
therefore, have not the power of perspiring, but compensate for this by
very rapid breathing. On the contrary, four-footed animals have glands on
many portions of the body. Nature is seldom contented with the one primary
function which an organ or tissue performs, but adjusts and adapts it to
others in many ingenious ways. Hence, when an animal perspires, the pores
of the skin allow the contained moisture to escape and moisten the surface
of the body; but in addition to this, in many animals, collections of
these pores in the shape of large glands secrete various odours which
serve important uses. In the skunk such a gland is a practically perfect
protection against attacks from his enemies. He never hurries and seems
not to know what fear is--a single wave of his conspicuous danger signal
is sufficient to clear his path.

In certain species of the rhinoceros there are large glands in the foot.
These animals live among grass and herbage which they brush against as
they walk, and thus "blaze" a plain trail for the mate or young to follow.
There are few if any animals which care to face a rhinoceros, so the scent
is incidentally useful to other creatures as a warning.

It is believed that the hard callosities on the legs of horses are the
remains of glands which were once upon a time useful to their owners; and
it is said that if a paring from one of these hard, horny structures be
held to the nose of a horse, he will follow it about, hinting, perhaps,
that in former days the scent from the gland was an instinctive guide
which kept members of the herd together.

"Civet," which is obtained from the civet cat, and "musk," from the queer
little hornless mu