Fowls are classed by modern naturalists as follows:
DIVISION. _Vertebrata_--possessing a back bone.
CLASS. _Aves_--birds.
ORDER. _Rasores_--scrapers.
FAMILY. _Phasianidae_--Pheasants.
GENUS. _Gallus_--the cock.
Birds, as well as quadrupeds, may be divided into two great classes,
according to their food: the Carnivorous and the Graminivorous. Fowls
belong, strictly speaking, to the latter.
In the structure of the _digestive organs_, birds exhibit a great
uniformity. The [oe]sophagus, which is often very muscular, is
dilated into a large sac--called the _crop_--at its entrance into
the breast; this is abundantly supplied with glands, and serves as a
species of first stomach, in which the food receives a certain amount
of preparation before being submitted to the action of the proper
digestive organs. A little below the crop, the narrow [oe]sophagus is
again slightly dilated, forming what is called the _ventriculus
succenturiatus_, the walls of which are very thick, and contain a great
number of glands, which secrete the gastric juice. Below this, the
intestinal canal is enlarged into a third stomach, the _gizzard_, in
which the process of digestion is carried still farther. In the
graminivorous birds, the walls of this cavity are very thick and
muscular, and clothed internally with a strong, horny _epithelium_,
serving for the trituration of the food. The intestine is rather short,
but usually exhibits several convolutions; the large intestine is always
furnished with two _corea_. It opens by a semicircular orifice into the
_cloaca_, which also receives the orifices of the urinary and generative
organs. The liver is of large size, and usually furnished with a
gall-bladder. The pancreas is lodged in a kind of loop, formed by the
small intestine immediately after quitting the gizzard. There are also
large salivary glands in the neighborhood of the mouth, which pour their
secretion into that cavity.
The _organs of circulation and respiration_ in birds are adapted to
their peculiar mode of life; but are not separated from the abdominal
cavity by a diaphragm, as in the mammalia. The heart consists of four
cavities distinctly separated--two auricles and two ventricles--so that
the venous and arterial blood can never mix in that organ; and the
whole of the blood returned from the different parts of the body passes
through the lungs before being again driven into the systemic arteries.
The blood is received from the veins of the body in the right auricle,
from which it passes through a tabular opening into the right ventricle,
and is thence driven into the lungs. From these organs it returns
through the pulmonary veins into the left auricle, and passes thence
into the ventricles of the same side, by the contraction of which it is
driven into the aorta. This soon divides into two branches, which, by
their subdivision, give rise to the arteries of the body.
_The jaws_, or mandibles, are sheathed in a horny case, usually of a
conical form, on the sides of which are the nostrils. In most birds, the
sides of this sheath or bill are smooth and sharp; but in some they are
denticulated along the margins. The two anterior members of the body are
extended into wings. The beak is used instead of hands; and such is the
flexibility of the vertebral column, that the bird is able to touch with
its beak every part of its body. This curious and important result is
obtained chiefly by the lengthened vertebrae of the neck, which, in the
swan, consists of twenty-three bones, and in the domestic cock,
thirteen. The vertebrae of the back are seven to eleven; the ribs never
exceed ten on each side.
The clothing of the skin consists of _feathers_, which in their nature
and development resemble hair, but are of a more complicated structure.
A perfect feather consists of the _shaft_, a central stem, which is
tubular at the base, where it is inserted into the skin, and the
_barbs_, or fibres, which form the _webs_ on each side of the shaft. The
two principal modifications of feathers are _quills_ and _plumes_; the
former confined to the wings and tail, the latter constituting the
general clothing of the body. Besides the common feathers, the skin of
many birds is covered with a thick coating of down, which consists of a
multitude of small feathers of peculiar construction; each of these down
feathers is composed of a very small, soft tube imbedded in the skin,
from the interior of which there rises a small tuft of soft filaments,
without any central shaft. These filaments are very slender, and bear on
each side a series of still more delicate filaments, which may be
regarded as analogous to the barbules of the ordinary feathers. This
downy coat fulfils the same office as the soft, woolly fur of many
quadrupeds; the ordinary feathers being analogous to the long, smooth
hair by which the fur of these animals is concealed. The skin also bears
many hair-like appendages, which are usually scattered sparingly over
its surface; they rise from a bulb which is imbedded in the skin, and
usually indicate their relation to the ordinary feathers by the presence
of a few minute barbs toward the apex.
Once or twice in the course of a year the whole plumage of the bird is
renewed, the casting of the old feathers being called _moulting_. The
base of the quills is covered by a series of large feathers, called the
_wing coverts_; and the feathers of the tail are furnished with numerous
muscles, by which they can be spread out and folded up like a fan. In
the aquatic birds--like the goose, the duck, and the swan--the feathers
are constantly lubricated by an oily secretion, which completely
excludes the water.
In their reproduction, birds are strictly oviparous. The _eggs_ are
always enclosed in a hard shell, consisting of calcareous matter, and
birds almost invariably devote their whole attention, during the
breeding season, to the hatching of their eggs and the development of
their offspring; sitting constantly upon the eggs to communicate to them
the degree of warmth necessary for the evolution of the embryo, and
attending to the wants of their newly-hatched young, until the latter
are in a condition to shift for themselves.
In the structure and development of the egg there is a great uniformity;
but there is a remarkable difference in the condition of the young bird
at the moment of hatching. In the class under consideration, the young
are able to run about from the moment of their breaking the egg-shell;
and the only care of the parents is devoted to protecting their
offspring from danger, and leading them into those places where they are
likely to meet with food.
The _longevity_ of birds is various, and, unlike the case of men and
quadrupeds, seems to bear little proportion to the age at which they
acquire maturity. A few months, or even a few weeks, suffice to bring
them to their perfection of stature, instincts, and powers. Domestic
fowls live to the age of twenty years; geese, fifty; while swans exceed
a century.
The order _Rasores_ includes the numerous species of _gallinaceous
birds_, and the term is applied to them from their habit of scratching
in the ground in search of food. They are generally marked by a small
head, stout legs, plumage fine, the males usually adorned with
magnificent colors, and the tails often developed in a manner to render
the appearance extremely elegant. The wings are usually short and weak,
and the flight of the birds is neither powerful nor prolonged. The
_corla_ of this order are larger than in any other birds.
The species are found in almost all parts of the world, from the tropics
to the frozen regions of the north; but the finest and most typical
kinds are inhabitants of the temperate and warmer parts of Asia. They
feed principally on seeds, fruit, and herbage, but also, to a
considerable extent, on insects, worms, and other small animals. Their
general habitation is on the ground, where they run with great celerity,
but many of them roost on trees. They are mostly polygamous in their
habits, the males being usually surrounded by a considerable troop of
females; and to these, with a few exceptions, the whole business of
incubation is generally left. The nest is always placed on the ground in
some sheltered situation, and very little art is exhibited in its
construction; indeed, an elaborate nest is the less necessary, as the
young are able to run about and feed almost as soon as they have left
the egg; and at night or on the approach of danger, they collect beneath
the wings of their mother. Most of these species are esteemed for the
table, and many of them are among the most celebrated of game birds.
The _pheasant family_, of this order, includes the most beautiful of the
rasorial birds; indeed, some of them may, perhaps, be justly regarded as
pre-eminent in this respect over all the rest of their class. In these,
the bill is of moderate size and compressed, with the upper mandible
arched to the tip, where it overhangs the lower one; the _tarsi_ are of
moderate length and thickness, usually armed with one or two spurs; the
toes are moderate, and the hinder one short and elevated; the wings are
rather short and rounded, and the tail more or less elongated and
broad, but frequently wedge-shaped and pointed. The head is rarely
feathered all over; the naked skin is sometimes confined to a space
about the eye, but generally occupies a greater portion of the surface,
occasionally covering the whole head, and even a part of the neck, and
frequently forming combs and wattles of very remarkable forms. In some
species, the crown is furnished with a crest of feathers.
The birds of this family are, for the most part, indigenous to the
Asiatic continent and islands, from which, however, several species have
been introduced into other parts of the globe. The Guinea Fowl of
Africa, and the Turkeys of America, are almost the only instances of
wild Phasianidous birds out of Asia. Some species, such as the Domestic
Fowl, the Peacock, the Turkey, and the Guinea Fowl, have been reduced to
a state of complete domestication, and are distributed pretty generally
over the world.