The Locomotor Appa/ratus. «S25 



or completes its revolution with a jerk. This condition 

 does not exist during life, nor after death until rigor mortis 

 occurs ; it is produced by the lateral ligaments of the hock- 

 joint, and is purely a post-mortem condition. 



The flexor metatarsi muscle is remarkable in having a 

 tendon running its whole length, so that from the origin 

 at the femur to the insertion at the front of the hock is a 

 stout tendinous cord. When the muscle acts the hock is 

 flexed, but the use of the tendon running from origin to 

 insertion is not at first sight quite clear. Chauveau con- 

 siders that it automatically flexes the hock, but tendons 

 are devoid of any such power ; and it appears to me that 

 its sole function is to relieve the muscle when the animal 

 is standing or sleeps standing. Though a flexor of the 

 hock, we must remember that when muscles which per- 

 form flexion and extension are acting together with equal 

 force no movement results. Such is the case when the 

 weight is on the limbs and the animal at rest. When a 

 horse is at rest his gastroc muscles and flexor metatarsi are 

 acting in opposite directions, and equally — the one is trying 

 to close the femoro-tibial angle, the other is keeping it 

 open; it is the function of the tendinous portion of the 

 flexor metatarsi to keep this angle open without any 

 muscular effort. 



Briefly reviewing some of the other joints, we find that 

 the Stifle is the largest in the body ; the cause of its rota- 

 tion has just been described. One chief function of this 

 joint is that of rendering the limb firm and rigid when the 

 foot is on the ground while the body is at rest, and this it 

 does by the contraction of the muscles inserted into the 

 patella ; if the latter bone be kept fixed on the upper part 

 of the trochlea of the femur, no flexing of the hock or stifle 

 can occur. This experiment can be readily tried on a horse 

 just destroyed ; the limb having been extended, the simple 

 pressure of the hand on the crural muscles is sufficient to 

 prevent the bending of the hock unless considerable force 

 be employed. No bending of the hock can occur if the 

 foot be kept extended ; the first movement in the advance 



