16 THE ANATOMY OF THE HORSE. 



human subject from its having two heads of origin. It is also known as the 

 flexor hrachii or coraco-radialis. It arises from the whole of the coracoid 

 process of the scapula with the exception of the tubercle on its inner 

 side, which is for the coraco-humeralis. Its strong tendon of origin 

 emerges from between the outer and inner tendons of the supraspinatus, 

 and passes over the shoulder-joint, a pad of fat separating its deep face 

 from the capsular ligament of the joint. The tendon, which is of fibro- 

 cartilaginous consistency, then plays over the bicipital groove of the 

 humerus, on which its deep face is moulded, and a synovial bursa 

 facilitates the movements of the tendon in the groove. The central 

 portion of the muscle, which is thick and fusiform, has numerous 

 tendinous intersections, and is traversed throughout by a fibrous , cord. 

 It rests on the anterior face of the humerus, and at its lower end 

 terminates by a tendon which, passing over the anterior ligament of 

 the elbow-joint (to which it is adherent), is inserted into the bicipital 

 tuberosity of the radius. The tendon is partly covered by the internal 

 lateral ligament of the elbow. The muscle has a second insertion, in 

 the shape of a strong fibrous band, detached from the main tendon to 

 blend with the sheath of the extensor metacarpi magnus, and deep 

 fascia on the front of the fore-arm. 



Action. — To flex the elbow-joint, and make tense the fascia of the 

 fore-arm. In the first of these actions it is a good example of a lever of 

 the third order, where the power is applied between the fulcrum — 

 represented by the elbow-joint, and the weight — represented by the 

 distal portion of the limb. The fibrous cord which traverses the 

 muscle is a mechanical extensor of the shoulder-joint, as long as the 

 elbow is kept extended by the triceps extensor cubiti. 



Directions. — The teres major from the shoulder upwards should now 

 be removed, in order to follow more thoroughly the course of the sub- 

 scapular artery with its branches, and to expose the small scapulo- 

 humeral muscle, which lies on the capsular ligament behind the joint ; 

 but care should be taken, in dissecting the tendons in the neighbour- 

 hood of the joint, to preserve the capsular ligament intact. 



The SuBSCAPULAE Abteet (Plate 6) springs from the axillary trunk 

 at the interstice between the subscapularis and teres major muscles 

 and disappearing from view, runs upwards at the posterior border of the 

 scapula. It gives ofi' as its most important branches : — 



1. A Muscular branch of considerable volume which passes backwards 

 and upwards on the deep face of the latissimus dorsi. 



2. The Posterior circumflex artery, which turns round behind the 

 shoulder, passing through a triangular space bounded by the teres major, 

 caput magnum, and scapulo-humeralis gracihs. At the outer side of 

 the joint (Plate 7) it appears between the caput magnum, caput medium, 

 and teres minor, and is covered by the deltoid. It splits into branches 



