264 



THE EXTERIOR OF THE HORSE. 



throughout its entire length to the previously-cited vertical axis. 

 This position of the member is the most favorable to the proper exe- 

 cution of its locomotory function, as we will verify a propos of the 

 vertical axes. It belongs, besides, to all properly-conformed horses, 

 whatever may be the service for which they are destined. 



The tibio-tarsal angle, under this premise, can be more or less open 

 according to the situation of the tibia which constitutes its superior 

 branch. Whence, consequently, there follow two secondary proposi- 

 tions with regard to the direction of the latter segment. 



1st. The Tibia, Straight. We will designate thus a tibia whose 

 obliquity is little marked (about 65 to 70 degrees). The hock which 

 corresponds to it is called straight; the angle which it forms is very 

 open (Fig. 79). A similar conformation is favorable to 

 velocity or speed, for it allows long strides, during which 

 the calcaneus becomes more and more perpendicular to' 

 the muscles that have to move it. Besides, the foot, on 

 arriving on the ground, is more strongly flexed upon 

 the leg, which gives the hock a more energetic and ex- 

 tensive impulsion. 



Running-horses ordinarily have this region thus 

 disposed; their tibio-tarsal angle is about 155 to 160 

 degrees, as we have already seen in treating of the leg. 

 The observer is easily deceived as to the width of 

 the straight hock on account of the direction which the 

 calcaneus here affects. On that account it is necessary 

 to observe the length of this bone during walking. 

 But it is an error to believe that this hock, implying 

 but little inclination of the tibia, necessarily violates 

 the vertical axis by placing the limb more under the 

 trunk. It suffices, to convince ourselves of the contrary, to observe 

 the thoroughbred horses, which have in nearly all instances a marked 

 opening of the tibio-tarsal angle, and to make measurements, as we 

 have done, upon their articular angles ; it will then be verified that 

 their axes are perfectly normal on account of the suitable direction of 

 the croup and the thigh. 



The straight hock, which it seems should produce much fatigue to 

 the animal from the little perpendicularity of its cord upon the cal- 

 caneus, is precisely so disposed in order that the deficient muscular 

 contraction may not interfere in a great measure. As H. Bouley 1 has 



FIG. 79. 



H. Bouley, loc. cit., p. 580. 



