ART ANATOMY OF ANIMALS
CHAPTER I.
GENERAL CONSIDERATIONS.
ART ANATOMY is a scientific explanation of the visible living form, or, in other words, it is the study of those parts of a living animal which influence its outward form or its expression. Besides the principal bones and muscles, this includes tendons, cartilages, sinew-sheaths, external veins and nerves, folds of skin, teeth, claws, beak, hoofs, horns, bristles, hair, feathers, &c.; and although it has been the custom of art anatomists to treat only of the first two mentioned, it will be seen that in many animals, the hair, and even the veins, are of far greater importance than many of the muscles or minor bones.
In depicting Birds also, a knowledge of the feathering is, generally speaking, of more value to the artist than familiarity with the separate muscles and bones. But a sound knowledge of the form of Mammals must be founded on an acquaintance with the bony skeleton and muscular system.
All Mammals are built on the same general plan; even the human form is but a slight variation of the same. All however are not equally good for study; some are poorly developed, some have the form obscured by wool, or by fat, some are too unwieldy or too minute, and others are not obtainable for study, through their rarity. But the Greyhound will be found well adapted to the requirements of the art anatomist, in his initial study of bones and muscles. It is superbly developed and the relation of its parts is admirably displayed through the fine skin and thin coat. It is neither too large nor too small, it is readily obtained almost anywhere, and when alive is perhaps easier to study than any other animal.
Natural sequence requires that the hairy coat be first treated or dissected. And it will be seen that this course is not entirely without justification in the importance of the subject.
Before proceeding further it will be well to give a word of warning regarding individual variation. In all departments of anatomy great allowance must be made for this, but especially in the muscles and the hair. It is probable, indeed, that the variations between a typical Dog and a typical Cat, Fox, Wolf, or Lion, &c., are not greater than those which will be found existing between different Dogs.
CHAPTER II.
THE HAIR.
Plates I, II, III., IV.
IT is remarkable that the study of the Hair should have been so long and so entirely ignored. In all animals that bear it, it is of interest and value, in most it is of equal importance with the muscles, in many it is of much more consequence than these, ranking in value next to the bones as an element of form.
In the Horse, or the Greyhound, we see the hairy coat at a minimum, and yet in these the Hair has much to do with their appearance. In a Wolf the hair-masses are at least of equal importance with the muscles, and in a Grizzly, or Brown Bear, in its winter coat, the hair-masses and the bones give the clue to nearly all the visible form. In a Barye statue of a bear now before me it is impossible to detect the form of a single muscle, except on the arm. All the rest of the detail is worked out in hair-masses.
In very small Mammals the turn of the Hair is almost the only clue to the form, and the peculiar rounding and cracking on ham and on shoulder are the only indications of the complicated machinery of bones and muscles which lies far beneath.
The Greyhound has too scanty a covering to be a good subject for an initial study of Hair, so the Common Wolf (Canis lupus) will be used instead. This animal, practically the same throughout North America, Europe, and Northern Asia, is really a Wild Dog, with the best possible development of a Dog’s powers. Its coat illustrates admirably all the essential features of furry covering, features which, though discoverable in the Greyhound, are in that animal so reduced as to be difficult of study.
The Hair of the Wolf and of most Mammals is of two kinds; a fine wool next the skin, and an outer covering of long, nearly straight hairs growing through this. The first retains the heat, and the second repels the rain. The first predominates on the lower and the second on the upper parts of the body.
The wool is also better than the hair for such parts as are very supple and change much in form, consequently we see a predominance of wool in those areas of loose or sliding skin under which the body has great play.
This may be due to the wearing off of the longer, brittler hair. The wool on these sliding areas is seen to crack open when the skin is extended. These peculiar tracts are so much more the result of arrangement than of actual change in the fur, that it is impossible to distinguish them in the animal after it is skinned or long dead; but no one can look at the living, moving creature and doubt their importance from a picturesque point of view.
These areas are limited in the Wolf, but in the Puma, or American Panther, we see them at a maximum, and the wonderful suppleness of this animal is aptly illustrated by the fact that its body is almost everywhere clad in this particular kind of covering.
The legs, shoulders, and face of the Wolf are covered by a variety of hair which is short, close and very hard. This is well calculated to give to the limbs and the senses perfect freedom of action, and at the same time is readily kept clear of mud, remnants of food, &c.
In general, the direction of the Hair is determined by two laws. First, the necessity of offering the least possible resistance to the air, and to grass, brushwood and other obstacles, while the animal is in motion. (This may be illustrated by the well-known fact that the hunter can readily drag, nose first, a dead deer which, heels first, he could scarcely move, for the obvious reason that it would be ‘ against the grain.’) Second, the necessity for running off the rain, especially while the animal is lying at rest. The first law gives a backward, and the second a downward direction to the Hair.
But these rules are much broken by local requirements of more force, as will be seen in the Wolf. The first important exception is the curious radiation of the hair about the eye, with the object of clearing the way for the sight. This divergence is well shown in the American Buffalo ; and among the feathered tribes, a notable parallel case is seen in the Owls. The hair of this radiation, meeting the counter-current of hair on the nose, produces the little ridge which is such a marked feature on the face of all hairy animals. (See Plates I., II., and III.)
On the side of the throat is a patch of reversed hair; it lies between the great thatch of the neck and the softer covering of the throat; it also covers the triangle between the upper and lower maxillary veins where they join the jugular.
This may be clearly seen in the Greyhound. (See Plate III.) After discussing with Dr. Caven the probable cause of this disturbance, we concluded that its history was briefly as follows :—
The early aquatic ancestor of living Mammals breathed by means of gills, which were gradually discarded as the creature became a land animal, and breathed by means of the elaborated air blad...