532 THE EXTERIOR OF THE HORSE. 



During the elevation, S, the trajectories are sensibly of the same nature as in 

 the trot, although farther separated from one another on account of the less flex- 

 ion of the articular angles. Yet those of the withers and the shoulder, and even 

 that of the elbow, remain almost horizontal. In the posterior member, the 

 coxo-femoral centre and the angle of the haunch describe a curve with the con- 

 vexity superior corresponding to the extension of the member before leaving the 

 soil. This is demonstrated by the chrono-photographs of Messrs. Marey and 

 Pages. 



Order of the Beats. It is most frequently the anterior mem- 

 ber which commences the step. The beats in such a case follow each 

 other in the following order, supposing the horse to step with the right 

 foot: 



Bight Diagonal Biped. 



1st beat : anterior right. 

 2d beat : posterior left. 



Left Diagonal Biped. 

 3d beat : anterior left. 

 4th beat : posterior right. 



When the animal leaves station in a position more or less camped, 

 it is sometimes a hind-member which moves first. If it be the left, 

 for example, the mode of succession of the beats remains the same, but 

 the fore-foot of the same side is brought down to the ground immedi- 

 ately afterwards. The step is then completed, as we have just said ; 

 the extremities then strike the soil in the following manner : left poste- 

 rior, left anterior, right posterior, right anterior, left posterior, etc., and 

 so on, as long as the gait remains regular. Duges l is consequently cor- 

 rect in stating that the " four legs of the horse may be represented to 

 the mind as two lateral pairs, acting the one after the other, and in each 

 of which the movement of the anterior member is always immediately 

 preceded by that of the posterior." 



Tracing and Notation. These facts, observed by ancient inves- 

 tigators on equine matters, have been registered automatically by the 

 apparatus of M. Marey. 2 We will reproduce (Fig. 224) the tracing 

 which he has obtained and the notation which corresponds to it. The 

 reader will in this figure find all the explanations necessary to compre- 

 hend its details. 



The following principal conclusions can be deduced from it : 



1st. The order of the beats, 1, 2, 3, 4, takes place after the mode indicated 

 above. 



2d. When one member is in the middle of its contact, that of the one which 

 follows it commences. 



3d. When one member is in the middle of its elevation, that of the one 

 which follows it commences. 



i Duges, Traite de physiologic compare, t. ii. p. 170. 

 Marey, La machine animate, p. 166. 



