THE HORSE IN MOTION. 91 



of gravity is given by one of the hind legs, and by that one which 

 is diagonal to the fore leg leaving the ground 'last; but, to reach 

 it in such manner as to prevent a catastrophe, it must be planted 

 beneath the centre of gravity or in advance of it, and then, in order 

 to prevent the anterior part of the body from falling forward, it is 

 necessary that all the available force should be brought to bear 

 upon the right hind leg as a lever with its fixed point upon the 

 ground. How this is effected, and by what muscles, is shown at 

 page 58. 



FIG. 



This situation is shown at Fig. 5. The picture was taken almost at 

 the instant of contact by the right hind foot with the ground. The 

 anterior portion of the body is arrested in its downward course, not 

 by its own limbs, but by the contraction of all the muscles forming 

 the external periphery of his body, from the neck to the flexors of the 

 foot ; by which combination of forces the whole body forward of the 

 head of the femur is not only arrested in its downward course, but 

 lifted, while the momentum in a horizontal direction is maintained 

 chiefly by the contraction of the vastus shortening the distance be- 

 tween the lower extremity of the femur and the spines of the sacrum, 

 pushing the pelvis forward from its fossa behind the head of the 

 femur. The body is propelled forward with a part of the same power 

 that lifts it. In this manner it does not check the momentum ac- 



