By this anticipation of a half-step (we have defined, p. 288, what is to be understood by the word _step_), it follows that when the marcher who is in front advances his right leg it is the left leg of the marcher who follows him that is carried in the same direction. We should thus conclude from this that the trot is characterized by a succession of displacements of the diagonal bipeds. [Illustration: FIG. 126.--THE TROT; RIGHT DIAGONAL PRESSURE.] [Illustration: FIG. 127.--THE TROT; TIME OF SUSPENSION.] Indeed, if we examine the notation of this gait (Fig. 125), we see that with the pressure of the right fore-foot is found associated the pressure of the left hind-foot. It is, accordingly, a typical diagonal biped (Fig. 126). [Illustration: FIG. 128.--NOTATION OF THE PACE OF STEPPING IN THE HORSE (AFTER PROFESSOR MAREY). L, Right lateral pressure; D, right diagonal pressure; L´, left lateral pressure; D´, left diagonal pressure.] But it is necessary to add that these groups of pressures do not succeed one another without interruption, except in the slow trot. In the ordinary trot, or in that in which the animal's strides are very long, the body between each of the double pressures which we have just been considering is projected forward with such force that it remains for an instant separated from the ground. This is what we designate by the name of _time of suspension_ (Fig. 127). The notation in this case would be slightly different from that which we reproduce above, in this sense: that between the diagonal pressures there then would be found an interval, since during the time the body is suspended none of the feet can produce a pressure-mark (see, with regard to these intervals, the notations of the running of a man, Fig. 118, and Fig. 119, 3, 4). =The Walk.=--Although slow, a feature which would seem to make it possible to permit its analysis in a horse when walking, this pace is difficult to comprehend without sufficient preliminary study. [Illustration: FIG. 129.--THE STEP: RIGHT LATERAL PRESSURE.] [Illustration: FIG. 130.--THE STEP: RIGHT DIAGONAL PRESSURE.] We saw above that in order to represent the amble the marchers had to move the legs of the same side simultaneously. We have also just seen that in order to represent the trot the marcher at the back had to anticipate by a half-step. Suppose, now, that this same marcher anticipates the man in front by a quarter-step only, or by a half-pressure period, and thus will be found realized the order of succession of the limbs in the gait or pace called the _walk_. The feet meet the ground one after the other, since they are each in advance by half the duration of a pressure. The strokes are four in number during the period of a step of this pace; in the amble and in the trot they do not exceed two, for then the limbs strike the ground in lateral diagonal pairs. [Illustration: FIG. 131.--THE GALLOP: FIRST PERIOD.] [Illustration: FIG. 132.--THE GALLOP: SECOND PERIOD.]