260 



] FORE LEGS. 



tinued down to the arm. Its office is to bend the head ; or, the head and necK being 

 fixed, to elevate and bring forward the arm. It is in powerful action when the horse 

 is running at his speed, with the head projected. 



At g is a portion of the sterno maxillaris, or muscle common to the fore part of the 

 chest and the lower jaw, and described at p. 159. 



h designates the principal portion of this muscJe, extending from the shoulder to the 

 humerus, and employed in drawing this bone towards the shoulder-blade, and bending 

 the whole of the limb. Exceedingly powerful action is required from this muscle ; 

 therefore it is very tendinous, and inserted in such a direction as to act with great 

 mechanical advantage, and that advantage increased in proportion to the slanting 

 position of the shoulder. 



The muscle ?', antea spinatus, is situated on the outer and anterior part of the shoulder, 

 below and behind the muscle next mentioned; and its office is to extend the humerus 

 on the scapula. It is also attached to the greater tubercle of the humerus, and to a 

 bony ridge extending from' it to the capsular-ligament of the shoulder-joint. Its 

 action is to assist in flexion of the humerus, and to give it a motion outwards. 



The muscle j\ postea spinatus, behind the spine or ridge, occupies that space of the 

 shoulder, and is inserted into the outer and upper head of the bone. It draws this 

 bone outward and upward. 



At k, is a muscle common to the breast and the shoulder-blade, and called the pec* 

 toralis parvus. It arises from the breast-bone, and reaches to the covering of the 

 shoulder-joint, and the muscles of the shoulder. Its action, in common with that of 

 a larger muscle, seen at m, the great pectoral, is to draw the head of the shoulder back- 

 ward, and also the lower part of the shoulder-blade, and to give the latter a more up- 

 right position. 



At q, is the tendon of a very important muscle, the extensor longus of the arm, 

 reaching from the upper angle and the posterior border of the shoulder-blade to the 

 point of the elbow and the inside of the arm, and which will be presently described. 

 At and s, are. the three divisions of another muscle concerned in the same office, 

 arising from the shoulder-blade and the lower bone of the shoulder, and likewise 

 attached to the point of the elbow by a very strong 

 tendon. 



This cut represents the muscles on the inside of the 

 shoulder and fore-arm, a is a very prominent one. It is 

 called the pectoralis transversua (the muscle crossing the 

 breast). It arises from the first four bones of the sternum, 

 and runs across to the inner part of the arm ; it is also 

 attached to the inferior part of the body of the humerus, 

 and to the fascia covering the arm, and reaching a con- 

 siderable way down the arm. The use of this muscle is 

 obvious and important. It binds the arm to the side oi 1 

 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 advantageous for the full 

 play of all the muscles concerned in progression. Con- 

 sidering 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 fore-legs spread out, and 

 the horse is " all abroad" the confused and unpleasant 

 manner of going, and the sudden falling-off in speed, are 

 well known to every rider. Mr. Percivall very properly 

 observes, that this muscle has probably more to do u 

 enablincr the arm to suDDort weight than to give i; 



enabling the arm to support weight 

 motion. 



THE HUMERUS, OR LOWER BONE OF THE SHOULDER. 



Forming a joint with the shoulder-blade, at the point of the shoulder, is the humerw 

 It is a short, strong bone, slanting backward in an opposite direction to the shoulder 



