194 THE EXTERIOR OF THE HORSE. 



the phase of elevation. When the first is stationary on the ground, 

 the second, or superior point, describes an arc of a circle and is 

 carried forward by the force of impulsion, and vice versa. 



At the moment when the foot, D (Fig. 54), is ready to leave the 

 ground, the line of direction, H'D, is inclined downward and back- 



FIG. 54. Schemes of the evolution of two congeneric members during the phases of contact and 



of elevation. 



ward. It is then advanced, describing an arc of a circle, and when it 

 reaches the point D' ', where it again touches its support, the line of 

 direction, H"D, is reversed. 



In the same half of the body (anterior or posterior) the phase, 

 DD f , of elevation of one member coincides always exactly with the 

 phase of contact, UHJ" of the other. The successive positions of one 

 member, whatever they be, are therefore directly the reverse of those 

 of its congener. As to the relative velocities of the transmis- 

 sion of the body and of the feet, they are different, but always 

 in simple relation. The foot, in the same space of time, passes over 

 a distance, DD', double that of the centre movement H'H". Its 

 velocity is therefore twice as great. 



Many years ago Captain Raabe 1 and M. Colin schematically rep- 

 resented the oscillations of the extremities in the following manner : 



Let us suppose that we examine the evolution of the posterior pair of limbs. 



The centre of the croup, If, during the phase of contact, describes a uniform 

 movement in advance which carries it from H to H', it being supported by the 

 right posterior limb, D. At this instant H', the right leg, is elevated, H'D, and 



1 Raabe, Examen du Trait6 de 1'exterieur du cheval, de Lecoq, et de la Physiologic, comparee, 

 de M. Colin, Paris, 1857. See, besides, the plates in the Traite de Physiologic, de M. Colin, t. i. 

 p. 445, 3e ed., Paris, 1886. 



