THE LOWER BONE OF THE SHOULDER. 



235 



into the tendinous substance cover- 

 ing the muscles of the forearm, and 

 reaching' a considerable way down the 

 arm. The use of this muscle is ob- 

 vious and important. It binds the 

 arm to the side of the horse; it keeps 

 the legs straight before the horse when 

 he is at speed, that the weight of 

 the body may be received on them in a 

 direction most easy and safe to the 

 horse and to the rider, and most ad- 

 vantageous for the full play of all the 

 muscles concerned in progression. 

 Considering the unevenness of surface 

 over which a horse often passes, and 

 the rapid turnings which are sometimes 

 necessary, these muscles have enough 

 to do : and when the animal is pushed 

 beyond his strength, and these muscles 

 are wearied, and the forelegs spread 

 out, and the horse is " all abroad,'' 

 the confused and unpleasant manner 

 of going, and the sudden falling oiF in 

 speed, are well known to every rider. 



THE LOWER BONE OF THE SHOULDER. 



Forming a joint with the shoulder-blade at the point of the shoulder 

 is the humerus, or lower bone of the shoulder (J. p. 63, and p. 230). It is 

 a short strong bone, slanting backward in an opposite direction to the shoul- 

 der-blade. At the upper part it has a large round head, received into the 

 shallow cavity of the shoulder-blade. It has several protuberances for the 

 insertion of muscles, and is terminated below by two condyles or heads, 

 which in front receive the principal bone of the arm between them as 

 in a groove, thus adding to the security and strength of the joint, and 

 limiting the action of this joint, and of the limb below, to mere bending and 

 extension, without any side motion. Farther behind, these heads receive the 

 elbow deep betv/een them, to give more extensive action to the arm. In 

 a well-formed horse this bone can scarcely be too short, in order that the 

 fore-legs may be as forward as possible, for reasons at which we have 

 already glanced ; and because, when the lower bone of the shoulder is long, 

 the shoulder must be too upright. Dislocation can scarcely occur in either 

 of the attachments of the bone, and fracture of it is almost impossible. 

 The lower bone of the shoulder, and the shoulder-blade, are by horse- 

 men confounded together, and included under the appellation of the shoul- 

 der, and in compliance with general usage we have described them as 

 combining to form the shoulder. 



Among the muscles arising from the lower bone of the shoulder, are 

 two short and very strong ones, seen at the lower r and s, the first pro- 

 ceeding from the upper part of this bone to the elbow, and the second from 

 the internal part, and likewise going to the elbow, and both of them bemg 

 powerful agents in extending the leg. 



In front, at y, is one of the muscles of the lower bone of the shoulder, 



