THE HORSE IN MOTION. 75 



ulna, or point of the elbow. It contracts synchronously with the 

 triceps, and its action is upon the capsular ligament to pull it out 

 of the way and prevent its being pinched in the elbow joint as it 

 becomes relaxed in the extension of the forearm. 



The muscles of the forearm are, like those of the posterior ex- 

 tremity, simple and direct in their action in extending and flexing 

 their levers, and, like those of the foot, their functions have been 

 well studied and are well known. But the complex forces are the 

 more difficult to understand the nearer we approach their sources, 

 and have led to great diversity of opinion ; the manner in which a 

 movement was produced could not be explained for the reason that 

 the motion itself was not understood. Now that the camera has ren- 

 dered those motions easy of analysis, it is not difficult to show how 

 they are produced. 



The corresponding angles being reversed, the anatomical relations 

 of the great flexors of the feet are changed. In the posterior limbs 

 their tendons passed over the angles of the hock to be inserted into 

 the bones of the feet. In the anterior extremities the corresponding 

 tendons are enclosed in a sheath of the strongest possible construc- 

 tion, into the outer wall of which the pisiform bone is placed, to afford 

 better protection to the tendons in the flexions of the knee joint, which 

 is double, so that when the flexion of one is completed it is continued 

 in the other, and greater flexion of the metacarpus upon the radius 

 is effected than would be possible were the joint single. It will be 

 noticed, on reference to the silhouettes, that the knee is never bent 

 when the corresponding foot is on the ground. It plays its part in the 

 role of a crutch consistently, but it performs a lively part in another 

 character when relieved from the weight of that responsibility. 



The tendons of the perforatus and perforans are utilized as liga- 

 ments as in the posterior extremities, but with some variations rendered 

 necessary by the different conditions. From the posterior surface of the 

 metacarpus, or cannon bone, below the knee, a ligament is thrown out 

 to the perforans tendon to reinforce it, and other ligaments or tendinous 

 connections are made to prevent extension of the joints beyond that 

 of the standing position, by which the tension is taken from the flexor 



