250 THE EXTERIOR OF THE HORSE. 



before or from behind. The reliefs of the anterior muscles in either 

 of these positions should be plainly marked and strongly convex out- 

 wardj When the leg possesses but little thickness, it then lacks force, 

 and is qualified thin, lean, flat, as we have seen above. 



Direction. The direction of the leg is as important a qualifica- 

 tion with regard to the development of force as to the production of 

 speed, for it favors the muscular action and facilitates the play of the 

 articular angles, according to its obliquity. It is measured by a line 

 joining two points situated the one above, the other below, the two 

 external tibial tuberosities, superior and inferior respectively. 



The direction of the leg, like that of the thigh, should fulfil two 

 principal requirements : 



1st. It should not alter the regularity of the vertical axis, which 

 axis affects the vertically of the canon and the tangency of the hock 

 to the vertical line which falls from the apex of the buttock. 



2d. It should secure a large opening and the proper direction of 

 the femoro-tibial and tibio-tarsal angles. 



A mean inclination of 65 to 70 degrees, according to our researches, 

 fulfils very well these conditions in swift horses. Indeed, instantane- 

 ous photographs demonstrate that the limit of extension of the tibial 

 section is situated very nearly on the vertical line which passes through 

 the centre of the coxo-femoral joint. Remembering this disposition, as 

 well as the fact that the femur is capable, during flexion, of surpassing 

 posteriorly the vertical line through its centre of movement, it is only 

 natural that the obliquity of the tibia should be more marked than 

 that of the femur. 



When the leg is too straight, which is rare, its degree of extension 

 is necessarily limited, and the step is short, whatever may be the length 

 of the thigh ; the foot, being too far forward, causes the horse to be 

 under himself behind. When it is too oblique, the flexion, on the con- 

 trary, is reduced, and the hock, being carried too far backward, pro- 

 duces the opposite defect, and the animal is said to camp behind. 



In speaking thus, we have supposed the direction of the femur and 

 the metatarsus to be invariable, for it will be understood that the former 

 of these segments, by modifying its inclination, might re-establish the 

 normal axis of the limb. But given a proper obliquity of the femur, 

 and, besides, the vertical direction of the canon as necessary, the posi- 

 tion of the tibia has a direct influence upon the axes and the degree 

 of aperture of the femoro-tibial and tibio-tarsal angles. Should it 

 become more vertical, it widens the angles, lengthens the member, 

 raises the trunk, diminishes the stability of the equilibrium, and 



