I06 TIIK IIOKSK IN MOTION. 



presents. All the plates show the horses approaching the barrier at a 

 run ; but no sooner is it observed than they begin to shorten their steps 

 and apparently measure its distance. In Plate XXVIII. the hurdle is 

 placed at an elevation of three feet six inches, and the horse betrays 

 his anxiety by shortening his paces, and advancing with both hind feet 

 nearly simultaneously and alternately with one fore foot, or what is 

 called prancing, until he has approached the barrier sufKiciently near 

 to satisfy himself that he can surmount it, when he plants his hind feet 

 well under the centre of gravity, and instantly the fore leg resting upon 

 the ground gives the thrust explained in Chapter IV., by which the 

 anterior portion of the body is raised, and the action is immediately 

 followed by all the muscles of the haunch, which project the body to 

 the required height. The anxiety and want of confidence of the 

 animal are betrayed by the nearness of his approach to the. obstacle 

 and the arrest of his momentum before he ventures the leap. By 

 the arrest of his momentum he has diminished the danger of injury 

 to the back tendons on reaching the ground again. 



In Plate XXIX. we see the same horse under somewhat altered 

 conditions. The hurdle is six inches lower, and he advances with 

 increased confidence, leaving the groimd eleven feet from it. 



The relations of the levers, or passive parts of the machine, in the act 

 of leaving the ground in leaping, are shown in Plate XXXV. Fig. i, 

 where the positions of the posterior extremity are the extreme of 

 extension. 



The next plate represents a full series of views by twenty-four cam- 

 eras, by means of which the movements in leaping are carried four feet 

 farther. The posterior extremities from the extreme of extension, on 

 leaving the ground, pass to the opposite extreme of flexion as they pass 

 the barrier, and both the posterior and anterior limbs, as they pass suc- 

 Cv^ssively in pairs, are so nearly in unison that they seem in the silhou- 

 ette to coincide. Plate XXXII. shows the same horse as seen in the 

 last preceding plate, after he has passed the hurdle and is nearing the 

 ground. The anterior extremities, that coincided in passing the hurdle, 

 are now separating in order that they shall not make contact with the 

 ground at the same time. One of the fore legs is extended as in the 



