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are technical expressions, and apply to the left and right sides of the animal. Another point to be attended to in examining the figures in question, is the relation which exists between the fore and hind feet of the near and oft sides of the body. In slow walking the near hind foot is planted behind the imprint made by the near fore foot. In rapid walking, on the contrary, the near hind foot is planted from six to twelve or more inches in advance of the imprint made by the near forefoot (fig. 21 represents the distance as eleven inches). In the trot the near hind foot is planted from twelve to eighteen or more inches in advance of the imprint made by the near fore foot (fig. 22 represents the distance as nineteen inches). In the gallop the near hind foot is planted 100 or more inches in advance of the imprint made by the near fore foot (fig. 23 represents the distance as 1101 inches). The distance by which the near hind foot passes the near fore foot in rapid walking, trotting, and galloping, increases in a progressive ratio, and is due in a principal measure to the velocity or momentum acquired by the mass of the horse in rapid motion; the body of the animal carrying forward and planting the limbs at greater relative distances in the trot than in the rapid walk, and in the gallop than in the trot. I have chosen to speak of the near hind and near fore feet, but similar remarks may of course be made of the off hind and off fore feet.
“At fig. 23, which represents the gallop, the distance between two successive impressions produced, say by the near fore foot, is eighteen feet one inch and a half. Midway between these two impressions is the mark of the near hind foot, which therefore subdivides the space into nine feet and six-eighths of an inch, but each of these is again subdivided into two halves by the impressions produced by the off fore and off hind feet. It is thus seen that the horse's body instead of being propelled through the air by bounds or leaps even when going at the highest attainable speed, acts on a system of levers, the mean distance between the points of resistance of which is four feet six inches. The exact length of stride, of course, only applies to that of the particular horse observed, and the rate of speed at which he is going. In the case of any one animal, the greater the speed the longer is the individual stride. In progression, the body moves before a limb is raised from the ground, as is most readily seen when the horse is beginning its slowest action, as in traction.” 1
At fig. 22, which represents the trot, the stride is ten feet one inch. At fig. 21, which represents the walk, it is only five feet five inches. The speed acquired, Mr. Gamgee points out, determines the length of stride; the length of stride being the effect and evidence of speed and not the cause of it. The momentum acquired in the gallop, as already explained, greatly accelerates speed.
“In contemplating length of strides, with reference to the fulcra, allowance has to be made for the length of the feet, which is to be deducted from that of the strides, because the apex, or toe of the horse's hind foot forms the fulcrum in one instant, and the heel of the fore foot in the next, and vice versâ. This phenomenon is very obvious in the action of the human foot, and is remarkable also for the range of leverage thus afforded in some of the fleetest quadrupeds, of different species. In the hare, for instance, between the point of its hock and the termination of its extended digits, there is a space of upwards of six inches of extent of leverage and variation of fulcrum, and in the fore limb from the carpus to the toe-nails (whose function in progression is not to be underrated) upwards of three inches of leverage are found, being about ten inches for each lateral biped, and the double of that for the action of all four feet. Viewed in this way the stride is not really so long as would be supposed if merely estimated from the space between the footprints.
Many interesting remarks might be made on the length of the stride of various animals; the full movement of the greyhound is, for instance, upwards of sixteen feet; that of the hare at least equal; whilst that of the Newfoundland dog is a little over nine feet.” 1
Locomotion of the Ostrich.—Birds have been divided by naturalists into eight orders :—the Natatores, or Swimming Birds; the Grallatores, or Wading Birds; the Cursores, or Running Birds; the Scansores, or Climbers; the Rasores, or
i Gamgee in Journal of Anatomy and Physiology, vol. iii. pp. 375, 376.
Scrapers ; the Columbce, or Doves; the Passeres ; and the Raptores, or Birds of Prey.
The first five orders have been classified according to their habits and modes of progression. The Natatores I shall consider when I come to speak of swimming as a form of locomotion, and as there is nothing in the movements of the wading, scraping, and climbing birds, or in the Passeres 2 or Raptores, requiring special notice, I shall proceed at once to a consideration of the Cursores, the best examples of which are the ostrich, emu, cassowary, and apteryx.
The ostrich is remarkable for the great length and development of its legs as compared with its wings (fig. 24). In this respect it is among birds what the kangaroo is among mammals. The ostrich attains an altitude of from six to eight feet, and is the largest living bird known. Its great height is due to its attenuated neck and legs. The latter are very powerful structures, and greatly resemble in their general conformation the posterior extremities of a thoroughbred horse or one of the larger deer--compare with fig. 4, p. 21. They are expressly made for speed. Thus the bones of the leg and foot are inclined very obliquely towards each other, the femur being inclined very obliquely to the ilium. As a consequence the angles made by the several bones of the legs are comparatively small; smaller in fact than in either the horse or deer.
The feet of the ostrich, like those of the horse and deer, are reduced to a minimum as regards size; so that they occasion very little friction in the act of walking and running. The foot is composed of two jointed toes, which spread out when the weight of the body comes upon them, in such a manner as enables the bird to seize and let go the ground with equal facility. The advantage of such an arrangement in rapid locomotion cannot be over-estimated. The elasticity and flexibility of the foot contribute greatly to the rapidity
1 The woodpeckers climb by the aid of the stiff feathers of their tails; the legs and tail forming a firm basis of support.
2 In this order there are certain birds—the sparrows and thrushes, for example-which advance by a series of vigorous leaps; the leaps being of an intermitting character.
3 The toes in the emu amount to three.
of movement for which this celebrated bird is famous. The limb of the ostrich, with its large bones placed very obliquely to form a system of powerful levers, is the very embodiment of speed. The foot is quite worthy of the limb, it being in
FIG. 24.-Skeleton of the Ostrich. Shows the powerful legs, small feet, and
rudimentary wings of the bird ; the obliquity at which the bones of the legs and wings are placed, and the comparatively small angles which any two bones make at their point of junction. a Angle made by femur with ilium. b Angle made by tibia and fibula with femur. C Angle made by tarsometatarsal bone with tibia and fibula. d Angle made by bones of foot with tarso-metatarsal bone. r Bones of wing inclined to each other at nearly right angles. Compare with fig. 4, p. 21, fig. 26, p. 55, and fig. 27, p. 59.-Adapted from Dallas.
some respects the most admirable structure of its kind in existence. The foot of the ostrich differs considerably from that of all other birds, those of its own family excepted. Thus the under portion of the foot is flat, and specially adapted for acting on plane surfaces, particularly solids. The
i Feet designed for swimming, grasping trees, or securing prey, do not operate to advantage on a flat surface. The awkward waddle of the swan, parrot, and eagle when on the ground affords illustrations.
extremities of the toes superiorly are armed with powerful short nails, the tips of which project inferiorly to protect the toes and confer elasticity when the foot is leaving the ground. The foot, like the leg, is remarkable for its great strength. The legs of the ostrich are closely set, another feature of speed. The wings of the ostrich are in a very rudimentary
FIG. 25.-Ostriches pursued by a Hunter. condition as compared with the legs. All the bones are present, but they are so dwarfed that they are useless as organs of flight. The angles which the bones of the wing make with each other, are still less than the angles made by the bones of the leg. This is just what we would a priori expect, as the velocity with which wings are moved greatly exceeds that with which legs are moved. The bones of the wing of the ostrich are inclined towards each other at nearly right angles.
1 In draught horses the legs are much wider apart than in racers; the legs of the deer being less widely set than those of the racer.
2 In the apteryx the wings are so very small that the bird is common spoken of as the "wingless bird.”