MOTION. 
leg moves rather oftener during the same pe- 
riod in trotting than in walking, or as 6 to 5. 
The velocity acquired by moving the legs in 
pairs, instead of consecutively, depends on the 
circumstance that in the trot each leg rests on 
the ground during a short interval, and swings 
during a long one, whilst in walking each leg 
swings a short, and rests a long period. The 
undulations arising from the projection of the 
trunk in the trot are chiefly in the vertical 
plane ; in the walk they are in the horizontal. 
In fig. 246, as designed by Bewick, and 
adapted to our purpose, we observe that the 
vertical line passing through the base of sup- 
port, lies not only behind the centre of gravity 
of the horse, but also of the centre of the mass 
of the rider, consequently the anterior legs 
will bear much the greatest proportion of the 
burthen. 
The gallop.—The gallop may be divided 
into three kinds, which may be distinguished 
by the number and order in which the feet 
happen to reach the ground. When the horse 
; ins the gallop on the right, the left hind leg 
_ reaches the ground first; the right hind and 
- left fore legs next, simultaneously, and the 
right fore leg last; this is termed the gallop of 
three beats. In the gallop where the four legs 
strike the ground successively, the left hind 
foot reaches the ground first, the right hind 
foot second, the left fore foot third, and the 
_ fight fore foot fourth ; ¢his is the gallop of four 
beats, but it is not the kind of movement 
adapted for great speed.* The gallop wherein 
the legs follow the same order as in the trot, 
—that is, the left hind and right fore feet reach 
the ground simultaneously, then the right hind 
and left fore feet ;—is the order in which horses 
_ move their feet in racing, where their greatest 
Speed is required, and is called the gallop of 
two beats.+ In the amble, the two legs on one 
_ Side rest on the ground, and _ propel the centre 
of gravity forwards, whilst those on the oppo- 
Site side are raised and advanced, and on 
taking a new position on the plane of motion, 
the former pair are raised and advanced in a 
Similar manner: these successive actions are 
accompanied by a considerable lateral motion. 
‘The amble is the pace peculiar to the Giraffe : 
* The gallop of four beats is often denominated 
“ the er.” i 
t See Sainbell. 
453 
in the horse it is only effected by artificial 
training. Borelli has erroneously described the 
order of the motions of the feet of the horse in 
walking; he states that the fore and hind feet 
on the same side move first, and then the fore 
and hind feet on the opposite side: these 
views, however, differ from the order as de- 
scribed by Aristotle,* and they have since 
been opposed by Barthez and Miiller, whose 
Opinions coincide with those which, after 
repeated observations, have been here intro- 
duced. In the gallop, the centre of gra- 
vity moves in a vertical plane, and describes the 
path of a projectile. The space passed over 
on the plane of motion is equal to the hori- 
zontal velocity of the centre of gravity multiplied 
by the time.t According to Sainbell, the cele- 
brated horse, Eclipse, when galloping at liberty, 
and with its greatest speed, passed over the 
space of twenty-five feet at each stride or leap, 
which he repeated 2} times in a second, being 
nearly four miles in six minutes and two se- 
conds. The race-horse, Flying Childers, was 
computed to have passed over eighty-two feet and 
a half in a second, or nearly a mile in a minute. 
Sainbell has given the geometrical proportions 
of Eclipse, together with the angles of in- 
clination and range of motion of the joints of 
the four extremities. He states that a consi- 
derable angle of inclination of the shoulder- 
joint, as well as an angular disposition of the 
limbs, are essentially necessary for great speed. 
Sir C. Bell,t however, states, “ that the speed 
of a horse depends on the strength of his loins 
and hind-quarters, and what is required in the 
fore-legs is strength in the extensor tendons ;” 
but surely this hypothesis cannot be correct, or 
the brewer’s dray-horse would be the fleetest. 
The horse is one of the most useful and most 
perfectly organized quadrupeds, combining 
great strength with speed. The length, strength, 
and angular disposition of the bones of the 
legs, the power of the muscles, the structure of 
the joints, the lengthened metatarsal and me- 
tacarpal bones, the consolidation of the pha- 
langes, and the structure of the expanded foot, all 
conspire to perfect the geometrical proportions 
of this valuable quadruped. 
Having now given in detail the various 
movements of the horse, we shall briefly pass 
to the other orders of Mammalia. 
Marsupialia.—In the Kangaroo, we observe 
a greater disproportion between the length of 
the anterior and posterior extremities than is 
found in any other quadruped, the length of the 
legs to that of the arms being as 383 to 174 
inches,§ or rather more than two to one. This 
* After the right of the fore feet they move the 
left of the hind feet. Afterwards they move the 
left of the fore feet and right of the hind feet. 
See Taylor’s Aristotle on the Progressive Motion of 
Animals, chap. xiv. 
+ See eq. 1. 
¢ Library of Useful Knowledge, Art. Animal 
Mechanics. . 
§ These measures are taken from a skeleton in 
the Hunterian Museum. Some variation will 
occur in the absolute length of the extremities, 
arising from the age and magnitude of the animal ;. 
but the ratio of the length of the extremities in the 
