26 THE SURGICAL ANATOMY OF THE HORSE 



between which structures it passes with the median nerve and the 

 posterior radial artery. It takes a course upwards behind the median 

 nerve, and on the inner aspect of the elbow unites with the ulnar vein 

 (32) and the basilic division of the median vein (31) (which has gained 

 the deeper level by piercing the posterior superficial pectoral muscle) to 

 form the brachial vein. 



T/ie Brachial Vein (24). — This large vein runs upwards, crossing the shaft 

 of the humerus obliquely. It is placed behind the brachial artery. It 

 receives the ulnar vein at the elbow joint at a lower level than the point 

 where the ulnar artery is given off. Towards the middle of the humerus 

 it receives the deep humeral vein (26), which joins the brachial on the 

 small head of the triceps extensor cubiti muscle. 



Near the upper extremity of the humerus it receives the prehumeral 

 vein (25), which appears from beneath the coraco-humeralis muscle and 

 runs transversely backwards across the humerus to join the brachial. 

 The severed end of the vessel is seen just below the position where it 

 becomes continued as the axillary vein. 



The Nerves 



The Brachial Plexus (7). — This flat fasciculus has been pinned down 

 to the inner face of the subscapularis muscle in order that the principal 

 nerves which supply the limb may be better displayed. The plexus is 

 formed by the inferior primary divisions of the sixth, seventh, and 

 eighth cervical and first and second dorsal nerves. It is tound in 

 the axillary space, surrounded by a considerable quantity of loose areolar 

 tissue. 



The Suprascapular Nerve (i i). — The fibres of this nerve come from 

 the sixth, seventh, and eighth cervical roots of the plexus. The nerve is 

 observed to disappear between the subscapularis and the supraspinatus 

 muscles where it curves round the coracoid edge of the scapula. It 

 supplies the supraspinatus and infraspinatus muscles. 



