CHAPTER I. THE FRAMEWORK OF THE HORSE CONSIDERED FROM A MECHANICAL POINT OF VIEW. THE skeleton of the horse is a very wonderful and beautiful piece of mechanism, which no one who takes an interest in such matters can contemplate without experiencing the pleasurable feeling that perfect harmony of proportion always inspires. We were about to add, fitness and adaptability to our purposes, but remembered, just in proper time, that this would be, after all, a very incorrect mode of expression; for, in truth, what is highly desirable is, that we should limit and adapt our requirements to the capabilities of this mechanism, and not simply to our own convenience, which but too frequently leads to abuse, as we shall now proceed to show. The horse depicted in Plate I.* is of an average description, and stands in a natural position, its head and neck stretched forwards, and the hind legs, instead of being perfectly perpendicular from the hocks downwards, slightly brought forward to assist in maintaining the equilibrium. The animal is at rest; there is nothing constrained in its attitude; but the eye tells us at once that a somewhat greater proportion of its weight * Taken from Seeger's 'System der Reitkunst.' rests on the fore legs than on the hind ones, owing, as one sees, to the projecting position of the head and neck, which are much heavier than the tail at the other extremity. Looking now at the spinal column, the framework of the back, on which the rider's weight is to be placed, we perceive that, whilst the under line of the vertebræ is nearly straight, although not quite horizontal, inclining somewhat downwards towards the forehand, the spinal processes of the first thirteen vertebræ of the back (dorsal vertebræ), reckoning from the point where the neck is attached, incline backwards, whereas those of the fifteenth, sixteenth, seventeenth, and eighteenth dorsal, and the six lumbar vertebræ, incline forwards; the fourteenth dorsal vertebra, with its process, standing perfectly upright, and forming, as it were, the keystone of the arch thus presented. It is very obvious that this inclination of the processes towards a central point is intended to and does limit the motion of the back downwards and upwards (i. e., vertically), so that, in fact, this fourteenth dorsal vertebra becomes the centre of motion of the horse's body-the point about which the several movements of the fore and hind legs are performed with various degrees of rapidity, either simultaneously or successively, and which constitute the paces of the horse; and this is further shown by the distribution and points of attachment of the muscles of the back and adjacent parts of the fore and hind quarters. Putting, therefore, the progressive movement of the animal out of the question as being equally applicable to all its parts, the internal motion of the several parts of the body increases in proportion to their distance from the fourteenth vertebra; and the same is applicable to burdens placed on the horse's back, especially a rider, whose frame is subject to its own peculiar motions, some of which are caused by the progressive movement of the bearer. It has been already pointed out, that in consequence of the projecting position of the head and neck, especially when the horse stands at ease, a somewhat greater proportion of its total weight falls on the fore legs than on the hinder ones; and when it depresses its head still more than is represented in Plate I.—for instance, for the purpose of grazing—the animal puts forward one fore leg, and usually at the same time the hind leg of the opposite side, for the purpose of securing its equilibrium; and even horses standing still, especially under a load, do the same, in order to rest each pair of legs alternately. We learn two facts from this: first, that the fore legs are essentially bearers, and that the hinder ones, although chiefly propellers, are also to a certain extent bearers; and, secondly, that a perpendicular line falling through the centre of gravity of a horse, as here represented, would lie nearer to the shoulder than the perpendicular E F, which falls through the centre of motion —that is, the fourteenth dorsal vertebra-and would probably cut the twelfth, or perhaps the eleventh, in some horses. Now, instead of going into the scientific detail of centres of gravity, which might prove difficult to some and tedious to most readers, we shall endeavour to render intelligible all that is really important to be known, by a very simple experiment that any one can repeat for themselves. a b c d, fig. 1, represents a piece of thin board 9 inches long by 4 inches wide, at whose corners four legs of about 7 inches long are |