Horse , a simple - hoofed, non-ruminating quadruped, constituting the soliped family of Cuvier's order of pachydermata, and, in Prof. Owen's system, the family solidungula, of the order perissodactyla (odd-toed), of the group ungulata (hoofed), and of the mammalian subclass gyrencephala (wave-brained). Zoologically considered, the family consists of the single genus equus (Linn.), distinguished from all other quadrupeds by having only one apparent toe and a single solid hoof on each foot, although under the skin, on the sides of the metacarpal and metatarsal bones, are the rudiments of two others on each limb. The dentition is : six sharp and cutting incisors in each jaw; six molars on each side of each jaw, with crowns of a quadrangular form, and having the surface intersected by deep plates of enamel arranged in four crescentic masses, and with a small additional disk of enamel on the inner border of the upper teeth; there are also, in the males, two small upper canines, and sometimes lower ones, usually absent in the females; there is a considerable space between the canines and the molars, opposite the commissure of the lips, which man has availed himself of to introduce the bit, by which this animal is subjugated to his uses; in the young animal there are also deciduous molars.

The different species of equus, as the zebras and the asses, so resemble each other in outward form and internal economy that the description of the typical species, the horse, will answer for all, with the exception of a few structural peculiarities; they are so nearly related to each other that they will breed together, producing more or less fertile hybrids, as in the cases of the horse and ass, and both with the zebra, etc. The skull of the horse is remarkable for the great width between the orbits, its flatness, the length of the face compared with the cranium, and the vertical depth of the lower jaw; the intermaxillarics project considerably beyond the nasal bones, the latter overhanging the cavity of the nostrils; the temporal arch is short, straight, and situated in the posterior third of the skull. The cervical vertebras are of large size, and the posterior arc oblong with short processes, so as to secure great freedom of motion in the neck; the dorsals are 18, with short transverse processes, and very long spinous anteriorly to afford origins for the ligament which supports the head; the lumbar are six (but five in the ass), broad and firmly joined together, with remarkably well developed processes, especially the transverse; the sacrum is a single bone, made up of five consolidated vertebra?, in a continuous line with the rest of the spine, and united to the last lumbar by the very large articulating oblique processes of the latter, securing a springiness in this region in leaping and galloping; the caudals vary from 17 to 21, having the form of vertebras only in the upper ones.

The chest is capacious, compressed laterally in front, and prolonged in advance of the first rib so as somewhat to resemble the thorax of a bird; in the middle and posterior portions it is rounded, and extends far back toward the pelvis; the ribs are 18 pairs, the anterior broad and massive (8 being true), and the posterior more slender. The clavicles are absent, and the coracoid process very rudimentary; the shoulder blades are triangular, with a prominent spine, closely approximated to the chest, transmitting the weight of this half of the body perpendicularly to the ground; the arm bone is short and strong; the forearm consists almost entirely of the greatly developed radius, the ulna being a mere appendage consolidated in the adult animal to its posterior surface, though its olecranon process is of large size, affording a powerful purchase to the extensor muscles; there are no movements of pronation and supination, but only of hinge-like flexion and extension. The carpus or wrist has seven bones in two rows, four in the upper and three in the lower; the metacarpus consists of a single long bone, the shank or cannon bone, and of two smaller supplementary pieces; this long bone represents the middle-finger metacarpal of the human hand, and the others the ring and forefinger metacarpals, those of the thumb and little finger being absent.

The fore foot is made up of three bones representing the three phalanges of a middle finger, called respectively the great and little pastern and coffin bones, the latter large and crescentic, supporting the hoof; there are also three sesamoid bones implanted in the flexor tendon of the foot. The pelvis is remarkable for the elongation of the ilium and the outward extension of the crest and spine; the thigh bone is massive, and so short that it is entirely concealed under the integuments of the trunk, what is commonly called the thigh being in reality the leg; the leg is formed almost entirely by the tibia, which is very strong at its upper portion, the fibula being a long slender bone among the muscles lost about the lower third of the tibia; the tarsus consists of six bones, the astragalus or cockal bone, the os calcis or heel bone, the cuboid, the navicular, and the middle and lesser cuneiform bones, the internal or great cuneiform being absent with the great toe which it supports; the metatarsus and the hind foot are constituted as in the anterior limb, and the bones have received the same names. The muscular system of the horse is very different from that of man, and has been described minutely in treatises on veterinary medicine.

The panniculus carnosus, of which the platysma myoides of man is a rudiment, is greatly developed and very movable, affording support and protection to various organs. The spinal muscles are of great extent and strength, especially in the neck and tail, which admit of much precision and grace of motion; the extensors of the forearm, the gluteus medius (the kicking muscle), and the muscles of the loins, extremities, and neck are generally very powerful; the muscles of the face, particularly those of the lips and nostrils, are largely developed, giving the well known variety of facial expression in this animal. The molar teeth of the horse may be known from those of other herbivora by the arrangement of the patches of enamel above referred to, and by their great length before they divide into fangs. The incisors are close together in a circle at the end of the jaws, slightly curved, with long simple fangs; the crowns are broad, thick, and short, of an elliptical form before they are much worn; a fold of enamel penetrates the crown like the inverted finger of a glove, which presents an island of enamel enclosing a cavity partly filled with cement and partly by the food; this is called the "mark," and is useful in determining the age of the animal, disappearing in very old horses, whose teeth get worn below the penetrating fold; according to Owen, it is usually obliterated in the middle incisors of the second set at the sixth year, and in the next and outer pairs in the seventh and eighth years respectively in the lower jaw, remaining longer in the upper, and in both its place is indicated for years by the darker color of the cement, even to the age of 16, after which the summits begin to assume a triangular form; the milk incisors are all shed before the age of five years.

The salivary glands, especially the parotid, are remarkably developed; the stomach is simple and capacious; the intestinal canal is long, but short in comparison with that of the ruminants; but the colon is of enormous capacity, as also is the caecum, apparently occupying the greater portion of the abdominal cavity; the small intestine is about 56 ft. long, with a circumference of from 2 1/2 to 6 in.; the caecum is 2 1/2 ft. long, and 2 ft. in circumference at the widest part; the colon and rectum are 21 ft. long, the former averaging 2 ft. in circumference; the whole canal, therefore, is about 80 ft. long. The liver weighs between 4 and 5 lbs., having no gall bladder, and the spleen 12 oz.; the urinary bladder is small in comparison with the size of the animal, its circumference when moderately distended being about 1 1/2 ft.; the mammary nipples are two, inguinal, and have at the base a hollow cavity which permits the accumulation of a considerable quantity of milk, which is often used by man as an article of diet, especially for invalids.

The hoof of the horse presents an admirable adaptation to secure solidity and elasticity in an instrument of progression; the whole exterior horny covering, to which the shoe is attached, composed of modified epidermic structure, is a hollow cone truncated above, into which the coffin bone is received; highest in front, it gradually diminishes backward, where it is suddenly turned inward, becoming mixed with the sole, supporting the under parts of the foot, and protecting the sole and the frog from too rough pressure against the ground; this internal wall, called the "bars of the foot," by its sloping direction, distributes the weight of the body toward the sides of the hoof, with whose numerous perpendicular horny laminae interdigi-tate similar processes from the vascular surface of the coffin bone. In the triangular space in the centre of the foot is an elastic horny mass called the frog, its base connecting the posterior curves of the hoof, the sides united with the bar, and the point extending about to the centre of the sole; on the sides are deep channels, to allow of its expansion and render the foot elastic; its actual thickness in horn is not so great as farriers seem to think, from the freedom with which they use the paring knife; in a well formed foot, the base of the frog ought to occupy one sixth of the circumference of the circle of the hoof; in the centre of the frog is a horny conical cavity of considerable depth, which protects the partially cleft foot from further rupture, adds to the elasticity, secures a firmer hold on loose soils, and passing above into the substance of the sensitive frog serves to unite firmly the two halves of the foot, which are completely divided in ruminants; this horny cone has been called the frogstay or bolt.

The sensitive frog falls into the inverted arch of the horny frog, which are thus held mutuary in place and preserved from external shock. The sole is an irregular plate of horn, closing up the lower opening of the foot, of an arched form, abutting everywhere against the sides of the wall, another contrivance for securing elasticity. The foot of the horse, therefore, though solid in front, is partially cleft behind, so that the terms solidungula and solipeda cannot strictly be applied to it; indeed a solid, continuous, unyielding circle of horn would be very painful if not entirely useless as an instrument of active progression; this beautiful structure, however, is sadly interfered with in almost all methods of shoeing. Immediately under the hoof are extensive cartilages, attached to the last two bones, protecting the upper part of the structure and adding greatly to the elasticity of the foot, and permitting the movements of the coffin bone with the hoof; in old horses these cartilages may become partially ossified, and are then called ring-bones. Under the hoof is also a very sensitive and vascular layer, from which the hoof originates, analogous to the soft core of hollow horns and the matrix of nails.

The eves of the horse are large, and the sight is excellent, and capable of distinguishing objects by night; the ears are large and very movable, and the sense of hearing is very acute, as in other timid and comparatively defenceless animals; the sense of smell is also acute, as is seen in their selection of food and in the recognition of their masters; the cutaneous sense is very fine, and the tactile powers of the movable lips exquisite. The food in a state of nature is exclusively vegetable. The time of gestation is about eleven months, and the foal in the domesticated state sucks six or seven months; the sexes are separated at two years; at three they may be broken, and at four be ridden. The disposition of the horse is naturally gentle and confident, which qualities have made it the most useful of animals in all the arts of peace and war; it is bold in the defence of its young, and occasionally an animal is vicious, either naturally or from bad treatment in youth. As we have horses varying in size from the Shetland pony to the Flanders dray horse, and in proportions from the thorough-bred racer to the Canadian cob, with every variety of color, so we find great diversity in their moral qualities; some are bold, intelligent, or good-natured, and others timid, stupid, or cross, and by care or from neglect each of these qualities becomes the characteristic of a race.

Their movements are many; besides the walk, trot, gallop, and amble, pace, or rack, some horses gallop with the fore legs and trot with the hind, others move each leg separately in succession, and others execute many artificial movements, the result of education. The horse is quick to perceive and has an excellent memory, two qualities which render his education easy; he is capable also of deep and lasting attachment. The neigh or voice of the horse is well known, the females exercising it less frequently than the males. The horse rarely lives to a greater age than 30 years, and is not serviceable for speed or very hard work for more than half this period. In compact form, elegance of proportions, and grace of movement, combining speed and strength, it is surpassed by no animal. Almost every part of the horse after death is useful to man; his skin is valuable for gloves, his hair for making cloth, his bones for buttons and for grinding into fertilizers, his flesh as food for hounds if not for man, his hoofs for making glue, and his intestines for the manufacture of delicate membranous tissues.

The experience of continental Europe has amply proved that horse flesh is a savory, nutritious, and wholesome article of food. - The original native country of the horse (equus ca-ballus, Linn.) is not certainly known; but he was most probably first brought under the subjection of man in central Asia or in the part of northern Africa adjacent to Nubia and Abyssinia. Useful as is the horse to man, the ass was preferred by nations of antiquity, from its easier management, hardier nature, and the cheaper food required to keep it in good condition; when greater wealth became common, the horse was more highly prized. Horses exist in the wild state in northern Asia and in America, the descendants of individuals formerly domesticated; in such cases they live in large troops, conducted in their wanderings and battles by an old male who has conquered the position of chief by superior strength and courage, and who, when his powers fail, is peacefully superseded by another. When danger threatens, they close their ranks, and present an unbroken circle of heels to the enemy, which is generally some of the larger carnivora.

The horse, whether originating in northern Africa or in northern Asia, probably exists nowhere at the present time in its original character; but wild horses, which have lived independently for many generations, entirely exempt from the influence of man, afford a tolerable idea of what the primeval animal was. Wild horses, as now met with, are generally smaller but more muscular than the domesticated ones, with less variety of color, stronger limbs, larger head, longer and less erect ears, more bushy mane, less sleek coats, and smaller and more pointed hoofs. When these troops fall in with domesticated horses, the latter almost always rush with them in a wild stampede and are irrecoverably lost. The wild horse, or mustang, even when adult, is readily brought to the domesticated state; the American Indians are very dexterous in taking them on the prairies and the pampas by means of lassos, and much of the wealth of many tribes consists in their herds of these animals roaming without any apparent control.

The wild troops have no fixed place of abode or of repose, frequenting the richest pasturages, and resting at night in dry and sheltered situations; they have great dread of storms and high winds, and a loud thunder clap will put them to flight in the utmost confusion and alarm. - Most countries have peculiar breeds of horses, adapted to the climate and wants of the region. In Arabia we find a horse remarkable for fleet-ness, endurance, and docility; its blood by intermixture has been made to improve other races of all sizes and constitutions, producing the breeds most highly valued both in Europe and America. The Tartar horses are small, hut hardy, accustomed to inclemencies of weather and scarcity of food, performing long journeys with great speed. The Persian horse is descended from the Arab, but is inferior in speed and less enduring; it was brought to England in the reign of Elizabeth, and by its cross produced an excellent breed. The Spanish breed, derived from the horse of Barbary, long enjoyed the highest reputation in Europe both for civil and military purposes; but they have now much degenerated from want of care. The Turkish horses have many characteristics of the Arab, from which they are descended.

The horses of Germany and France have been modified by all the above breeds, and are very hardy; the Dutch breed are very large, and excellent for draught. The English have paid the most attention to the breeding of horses, and have surpassed all other nations in the quality of speed; the English racer is unequalled for quickness and endurance, in which respects he exceeds the best horses of the original oriental stock. America has taken advantage of the best breeds of the old world, and can compare favorably with any country; her trotting horses have no superiors in their peculiar gait. The race horse is the product of the Arabian with the native English breed, commenced by James I., improved by Charles II., who imported barbs and Turkish stallions, and crossed by the Darley and Godolphin Arabian. Crossing the thoroughbred with cold-blooded mares produces the more strong-limbed varieties used as carriage horses, roadsters, chargers, and cavalry horses. Another race is seen in the different kinds of dray horses, remarkable for strength, intelligence, and docility. - There is no doubt that the horse was unknown to the natives of America at the time of its discovery by Europeans, and it is certain also that the animal inhabited this country during the postplio-cene period, contemporaneously with the mastodon and mcgalonyx; its fossil remains, chiefly molar teeth, have been so frequently found, especially in the southern and western states and in South America, and have been so carefully examined by competent palaeontologists, that no doubt can remain of the former existence of the horse in the western world.

The E. neogoeus (Lund) and E. major (De Kay), two species of the closely allied genus hipparion, and one of hippotherium, indicate that the equine family were well represented in America in former geological periods; whether this ancient horse, of about the same size as the recent one, and distinguished by the usually more complex folds of the enamel of the molars, became entirely extinct before the appearance of man, may admit of question. Prof. Leidy says there is no room to doubt the former existence of the horse on the American continent, at the same time with the mastodon, and that " man probably was his companion." The fossil horse has also been found in the old world, in the pliocene of Europe with the mastodon and tapir and through all the diluvial period, and in the upper tertiary of Asia; there are two or three species described in Europe, and as many in Asia. From this it appears that the horse inhabited the old world as well as the new before the advent of man; and some of these antediluvian species may have become extinct, while others persisted in a declining condition during the early part of the human epoch. (See Hipparion.)

Shetland Pony.

Shetland Pony.

Mustang.

Mustang.

Arabian Horse.

Arabian Horse.

English Race Horse.

English Race Horse.