LOCOMOTOR SYSTEM 619 



One stride at a walk contains two steps ; in any faster pace than 

 the walk the stride embraces a period in the air, during which 

 there are no feet on the ground. In the trot, the legs being used 

 in diagonal pairs, there are two steps and two springs to the 

 stride ; in the canter and gallop there are two steps and one 

 spring. 



Limb Velocities. — It must not be forgotten that in the slowest 

 paces the legs in motion are moving faster than the horse. Take 

 the case of the walk at five miles an hour : the moving legs have to 

 overtake the body, and in order to do that within the brief period 

 allowed they must move at least double as fast as the horse. In 

 the gallop Muybridge showed that a horse covering nineteen yards 

 in a second (thirty-nine miles an hour nearly) the advancing limb 

 was brought forward with an occasional velocity of forty yards 

 a second, or nearly eighty-two miles an hour. It is not a matter for 

 surprise that so much doubt and difficulty existed before the intro- 

 duction of instantaneous photography. 



The ordinary exposures given by Muybridge were the one-thou- 

 sandth part of a second, though much shorter exposures than these 

 were also employed. During the one-thousandth part of a second 

 a horse galloping as above may move forward f^ inch, and the 

 moving foot i| inches, so that shorter exposures had to be em- 

 ployed for high velocities. 



Even when the order and method of moving the limb is known, 

 it is very difficult, excepting in the slowest paces, to catch a glimpse 

 of the real movement in any other pace than the trot. The limbs 

 are as confusing as the spokes of a rotating wheel, while the body 

 of the horse itself helps in no slight way to divert attention. To 

 obviate this the writer finds that the best method of seeing the limbs 

 working is by looking at them through a narrow slit in a card, so held 

 that only the legs are seen through the slit and the body cut off. 



The paces commonly employed by the horse are the walk, 

 trot, canter, and gallop. There are others, such as the amble 

 and the rack, neither of which are popular in this country, nor, 

 indeed, is the latter employed for any other purpose than in one 

 form of American racing. In all these paces the limbs are em- 

 ployed in different combinations. In the walk, for instance, a 

 broad base of support is required, so that during a stride for half 

 the time there are two legs and half the time three on the ground 

 at one and the same moment. In the trot for half the time there 

 are two legs on the ground and half the time the body is in the 

 air. The arrangement is different in the canter, and again differ- 

 ent in the gallop. Each pace has its own system of combinations, 

 and when all the possible combinations are classified they amount 

 to fourteen for the four legs. For intance, the number of different 

 ways in which a single limb may be employed is obviously four, 

 the possible combination with two legs is six, and the various 

 combinations with four legs employed in progression is fourteen. 



