MUSCLES. 



43 



neck ; and its other end to the first eight ribs. Some anatomists 

 call its anterior portion the angularis muscle of the scapula (levator 

 anguli scapulcB of man). When the front portion contracts, the 

 shoulder-blade is drawn forward ; when the rear portion contracts, 

 this bone is pulled back. This muscle, from the manner of its attach- 

 ment, acts as a sling for the fore limb. The upper part of the shoulder- 

 blade is connected to the trunk, from its inner extremity by a muscle which 

 has one end attached to the suspensory ligament of the head and neck, 

 and the other to the withers. Hence, on contracting, it draws the 

 shoulder-blade forward and ujnvards. The outside of the shoulder-blade 

 is connected to the trunk, at about its upper third, by a muscle which 

 has one branch going to the withers, and the other to the suspensory 

 ligament of the head and neck. It can thus raise the shoulder-blade, 

 or work it backwards or forwards. The fore limb is drawn forward chiefly, 

 however, by the action of a muscle {levator humeri) which is attached, 

 at one end, to the top of the head and first four neck vertebrae, and 

 b}' the other to the middle of the humerus. We may see from the 

 foregoing remarks, that length of neck and height of withers are 

 favourable conditions for the firm attachment of the shoulder-blade 

 to the trunk and for the free action of the shoulder. 



The fore limb is connected to the breast-bone by a muscle which is attached 

 to the breast-bone and humerus. 



The fore limb is drawn back, principally, by two muscles, one of which 

 is attached, at one end, to the abdominal tunic (p. 40) and breast- 

 bone ; and at the other, to the humerus and shoulder-blade, close to 

 the shoulder joint. The other muscle (the latissimus dorsi) has its 

 origin on the vertebrje of the loins and back, and is inserted on the 

 humerus, which it consequently draws backwards and upwards when 

 it contracts. The first mentioned muscle tends to draw it backwards 

 and downwards. 



Muscles of the fore limb. — When a fore leg is advanced, the shoulder 

 joint is extended and the elbow joint flexed. When it is drawn back, the 

 0]5posite to this takes place. Agreeably to these actions, we find a power- 

 ful muscle (flexor brachii) attached, by one end, to the front part of the 

 shoulder-blade, just above the joint ; and by the other end to the front of 

 the radius immediately below the elbow joint, so that, when it contracts, 

 it extends the shoulder and flexes the elbow. Another muscle, being at- 

 tached to the rearmost corner of the shoulder-blade and to the point of 

 the elbow, flexes the shoulder and extends the elbow. Besides these 

 muscles, there are various others which respectively aid in the Hexion 

 and extension of these joints. The chief muscle that extends the knee 

 has its origin on the front part of the humerus, just above the elbow 

 joint, and running down the fore-arm, is joined to its tendon, which 

 passes over the knee, and which is inserted on the head of the cannon- 



