replaces them in due order. Domestic birds are not furnished with so large a portion of this fluid as those which live in the open air. The feathers of the former are pervious to every shower, while Swans, Geese, Ducks, and all those which live upon the water, have their feathers dressed with the oil from the first day of leaving the shell: where this oil abounds, it usually renders the bird rank, and sometimes very unpalatable as food.

THOMSON, in his Spring, thus alludes to this oleous unction:

"Hush'd in short suspense,

The plumy people streak their wings with oil,
To throw the lucid moisture trickling off,

And wait the approaching sign to strike at once
Into the general choir."

These oleous glands become sometimes diseased and tu mefied; the complaint is commonly denominated the Pip. It is generally remedied by a simple puncture, by which the collected fluid may be discharged.

The BONES of birds vary in many particulars from those of the mammalia. The chief difference, however, is, that of the Sternum or BREAST-BONE, which covers not only what is called, in the mammalia, the thoracic viscera, but also a considerable portion of the rest of the intestines. This bone, in all the birds which fly, is distinguished by a long ridge or keel, to which muscles may be and are attached, to facilitate their flight; that this keel is for such purpose there can be no doubt, as in birds which do not fly, the Ostrich for instance, the keel in the sternum is altogether wanting. The cervical vertebræ are also much more numerous in birds than in the mammalia, arising, of course, from their greater length of neck. And the rings in the

Trachea, which in man do not amount to twenty, in the Ostrich lately dissected at the Zoological Society, it was about four feet long, and the rings in it were more than two hundred. The sternum in the Ostrich is not only without the keel, but it is exceedingly small when compared to its size in that of other Birds.

Although Birds have only two legs, yet the bones of their wings, when examined anatomically, correspond in a great degree with the fore limbs of many of the mammalia. It is chiefly in their use and covering that they differ from quadrupeds and man. But the bones of Birds differ in another particular, namely, they are most of them hollow, and have communication with the air cells in their bodies, by which they are rendered more buoyant.

Birds have no external ears, a few of the Owl tribe excepted, although their organs of hearing are, beyond question, acute, as their various notes and modulations of sound sufficiently evince. It has, however, been supposed, that they have no idea of harmony, as they never sing in concert ; they nevertheless imitate sounds with great facility; so much So, indeed, that Mr. BARRINGTON (see below,) thinks all the notes of song birds are imitations. It is chiefly, I apprehend, on this sense, and on that of sight, that birds depend for their safety and preservation. The touch, taste, and smell, being in the generality of the tribe of a secondary order.

The organ of smell is said in the Gannet to be wanting; but, in most birds, there is no reason to think that the organ is absent; yet, notwithstanding it has been generally supposed that this sense is active in the rapacious tribes, particularly the Vulture, some late observations seem distinctly to show that, in the pursuit of his prey, the Vulture is guided by his sight rather than by his smell. Still there is reason to believe, that many of the rapacious tribe are

D

assisted in discovering their prey by the sense of smell. See forwards an anecdote of the Eagle related by Mr. Brookes.

While the touch, taste, and smell, of Birds generally, are certainly not of the first order, their sight is extremely acute. The Hawk, and others of the Falcon genus, can, at a considerable distance, discern an animal, a lark, or a mouse, upon the ground, and pounce upon it with celerity and certainty.

Anatomists have, it is said, observed in the eye of Birds a particular expansion of the optic nerve, which renders the impression of visible objects more vivid and distinct. To protect the eye, and, perhaps, also to moderate its extreme sensibility, this organ is furnished in many birds with what is called a nictitating membrane, with which the bird can, at will, cover the pupil of the eye while the eyelids remain open; and hence the Eagle, and some other birds, are enabled to bear, by the assistance of this covering, the strongest light of the sun.

Birds have neither epiglottis, diaphragm, urinary bladder,

nor scrotum.

The lungs, which are two red, oblong, spongy bodies, attached in the thorax chiefly to the spinal column, are not divided into lobes; they are covered with a membrane, or pleura, which communicates by many openings with large vesicles or air bags, that are dispersed over the abdomen as well as the thorax. By these, birds can, at pleasure, render their bodies more buoyant, and thus ascend to a considerable height, or skim along in the air with a celerity that far outstrips the swiftest steed. The cavity of the thorax of birds is much larger in proportion than that of other animals, much of which is not filled with the lungs, but with air. This, and the thin porous nature of their bones, many of which are filled with air instead of marrow,

and in several instances communicate directly with the lungs, add, of course, to their facility of flight. Even the bones of the Ostrich, although this bird cannot fly, are hollow; and he is also furnished with air vesicles similar to other birds, which, notwithstanding he cannot leave the earth, enable him, by the assistance of his powerful and muscular legs, to run with astonishing swiftness, Mr. GREEN informed us in his Lectures on the comparative anatomy of Birds at the College of Surgeons, (April, 1827,) that in young birds a medullary substance was often observable in the bones, but that, as they grew up to maturity, it became absorbed, and the bone empty.

It may be stated, too, that the blood of Birds is generally of a brighter colour, and warmer, than that found in the mammalia, and that it circulates with much more rapidity. While the Horse has about forty pulsations in a minute, man from seventy to eighty, in Birds they vary from one hundred to one hundred and ten. From the extreme mobility and activity of Birds, it would seem that they are more highly oxygenated than other animals; in addition to which it may be mentioned, that Birds consume more food in proportion to their size, in a given period, than any other race of animals.

Perhaps, however, one of the most striking peculiarities in the anatomical structure of Birds is the stomach. In those whose food consists principally of grain and seeds, the stomach is cartilaginous, and covered with very strong muscles in this state it is called a gizzard. This structure is necessary, in order that, by its strong action, the food should be comminuted; but, besides this, birds with such stomachs pick up and swallow, occasionally, small gravel stones, which assist the process of comminution. In a state of nature, the quantity of gravel taken in is regulated, no

doubt, by the sensation of the stomach; but in domesticated animals this faculty is sometimes deranged. Young Ducks have been known to take so much gravel as to produce death.

On the contrary to those Birds that are carnivorous or piscivorous, a membranaceous stomach is given, which more resembles that of carnivorous quadrupeds; the digestion of such Birds being more accelerated by the gastric juice than by the action of the stomach itself.

Those Birds belonging to the first class digest or retain every substance taken in; and those which eject or disgorge innutricious matter unavoidably taken in, such as feathers, fur, bones, &c. belong to the second class, conspicuous in the Eagle and Owl tribes, and those also that feed on fish. The innutricious matter, termed Castings, which is ejected by Eagles, Owls, &c. descends most probably no farther than the crop in which the nutritive from the innutritive portion of the food is separated.

It ought also be mentioned, as a remarkable fact, that the rapacious birds seldom or never drink. Eagles, Hawks, and Owls, were kept by COLONEL MONTAGU for years without tasting water.

Besides the stomach, most Birds have a membranous sac, capable of considerable distension; it is usually called a CROP, (by the scientific Ingluvies,) into which the food first descends after being swallowed. This bag is very conspicuous in the granivorous tribes immediately after eating. Its chief use seems to be to soften the food before it is admitted into the gizzard. In young fowls it becomes sometimes preternaturally distended, while the Bird pines for want of nourishment. This is produced by something in the crop, such as straw, or other obstructing matter, which prevents the descent of the food into the gizzard. In such