curves of pressure of the four feet, drawn at two different levels: the uppermost are the curves of the anterior limbs; those below, of the posterior limbs. In each series the curves of the left foot are drawn with dotted lines, those of the right with full lines.

FIG. 5.-GRAPHIC CURVES AND NOTATION OF THE HORSE'S TROT.-R A, reactions of the fore-limbs; R P, reactions of
the hind-limbs; A G and A D, curves and notations of fore-limbs; PD and P G, curves and notations of bind-limbs.

The moment when the curve begins its rise represents the commencement of the pressure of the foot on the ground; the point at which the curve begins to descend represents the moment when the rise of the foot commences. It is seen from these tracings that the feet AG and PD, left fore-foot and right hind-foot, strike the ground at the same time. The simultaneous lowering of the curves of the two feet shows that they also rise from the ground simultaneously.

Under these curves is placed the notation which represents the pressure of the left diagonal biped. The second impact is given by the feet AD and PG (right diagonal biped), and so on through the whole length of the tracing. Thus the free trot is a pace in which all the four feet give but two strokes, and in which the ground is struck in turn by the two diagonal bipeds; it is also a high pace, the animal being raised for a brief interval between two successive strokes above the ground. The duration of this suspension, according to Fig. 5, is equal to half the time the feet are pressing on the ground. But the

trot varies greatly in different horses in this particular, there being oftentimes a very slight period of suspension, although a perfect synchronism of the diagonal strokes of the feet is observed.

By comparing the lines illustrating the reactions with the tracings afforded by the movements of the limbs, it will be seen that the mo

FIG. 7.-HORSE TROTTING WITH A LOW KIND OF PACE.-The instant corresponding with the attitude represented in this figure is marked with a white dot on the notation.

ment when the body of the animal is at the lowest part of its vertical oscillation coincides precisely with that at which its feet touch the ground. The time of suspension does not depend on the fact that the

body of the horse is projected into the air, but upon the fact that all four legs are bent during this short period. The maximum height of the suspension of the body corresponds, on the contrary, with the end of the pressure of the limbs on the ground. It is also seen that the reactions of the fore-limbs exceed those of the hind ones. This inequality appears to be constant, and is still more marked in the walking-pace.

We have learned that one of the chief characteristics of the free trot is the entire synchronism of the strokes of each diagonal biped. There is a form of this pace, however, called by M. Marey the irregu lar trot, where such synchronism is wanting, the hind limb of one or both diagonal bipeds striking the ground an instant later than the corresponding fore-limb. Fig. 6 represents the notation of the irregular trot. The stroke of the left fore-foot is seen to be a little earlier than that of the right hind-foot, and the same is true of the limbs belonging to the right diagonal biped.

The low and short trot is represented in Fig. 7. The diagonal impacts succeed each other without interval, as may be seen in the

notation placed below the figure. The animal has been depicted from the notation. The instant which the artist has chosen is that marked in the notation by a white dot. At this moment, as the superposition indicates, the left fore-foot is at the end of its pressure; the right fore-foot is about to reach the ground; the right hind-foot is finishing its pressure, and the left hind-foot is about to fall.

The elevated and lengthened trot is represented in Fig. 8. The animal is depicted at the instant which in the notation is represented by a dot; that is to say, during the time of the suspension, at the moment when the left diagonal biped has just risen, and the right diagonal biped is about to descend.

Tracings afforded by the walking-pace are shown in Fig. 9. If we let fall a perpendicular from the points at which the curves commence, we shall have the positions of the successive impacts of the four legs. The order of succession of impacts is represented by the letters AD, PG, AG, PD, that is to say, right fore-foot, left hindfoot, left fore-foot, right hind-foot. The notation of the rhythm of the pressure of each foot, as derived from the registered curves, shows that the interval which separates the impacts is the same throughout, and consequently that the horse rests during the same time on the lateral as on the diagonal bipeds. This, however, is not always the case, some horses resting longer on the lateral biped than on the diagonal, and vice versa. The change of position of the centre of gravity may be seen by reference to Fig.

FIG. 9.-TRACINGS AND NOTATIONS OF THE WALKING-PACE, WITH EQUAL PRESSURES OF THE FEET, BOTH DIAGONALLY

AND LATERALLY.

9.

From 1 to 2 the horse will rest on the right lateral biped; from 2 to 3 on the right diagonal biped (that is to say, on that in which the right foot comes first); from 3 to 4 on the left lateral biped; from 4 to 5 on the left diagonal biped; again, from 5 to 6 the horse would find himself, as at the beginning, on the right lateral biped.

Observations on draught-horses have shown that, when the animal

strives to react against a load, he may have three feet on the ground at once. This is held by some to be the rule in the normal walkingpace, but M. Marey has proved to the contrary. The vertical oscillations of the walk are chiefly at the withers, those of the croup being very slight. The actions of the hinder parts seem to consist chiefly

in a forward propulsion, with a scarcely perceptible impulsion of the body in an upward direction. This agrees with the theory quite generally admitted, that the fore-legs have little to do in the normal pace, except to support alternately the fore-part of the body, while to the hind-limbs belong the propulsive action and the tractive force exerted by the animal. Fig. 12 is a representation of the horse at a walkingpace. The instant is marked in the notation by a dot.

The gallop comprises all those paces in which irregular impacts of the feet upon the ground recur at regular intervals. Most writers distinguish three kinds of gallop by the rhythm of the impacts, and name them, according to this rhythm, gallop in two, three, and four time. The most common kind is the gallop in three-time, from which the tracings in Fig. 11 have been obtained. At the commencement of the figure the animal is suspended above the ground; then comes the impact P G, which announces that the left hind-foot touches the ground. This is the foot diagonally opposed to that which the horse places forward in the gallop, and whose impact A D will be the last produced. Between these two impacts and in the middle of the interval which separates them, comes the simultaneous impact of the two feet forming the left diagonal biped. The superposition of the notations AG, PD, clearly shows this synchronism. In this series of movements the ear has therefore distinguished three sounds at nearly equal intervals. The first sound is produced by a hinder-foot, the second by a diagonal biped, the third by a fore-foot. Between the single impact