THE LIMBS OF THE HORSE 21 



N. EADIALIS. — Nearly or quite as large as the median, the radial ^ 

 nerve leaves the more caudal part of the brachial plexus, accompanies 

 the ulnar nerve, and, about the middle of the arm, disappears between 

 the long and medial heads of tlie triceps. Before disappearing from 

 the present dissection, the nerve furnishes a branch to the tensor of 

 the antibrachial fascia ; and it is generally possible to see the origin 

 of the nerves to the long and medial heads of the triceps. 



N. ULNAKis. — Smaller than the radial or the median, the ulnar ^ 

 nerve passes into the arm between the axillary vessels and the radial 

 nerve. About the middle of the arm it forsakes the vessels and runs 

 obliquely between the triceps and the tensor of the antibrachial fascia, 

 to enter the forearm between the olecranon and the medial epicondyle 

 of the humerus. About the middle of the arm it also gives off a 

 cutaneous branch (ramus cutaneus volaris), which crosses the surface 

 of the tensor fascia antibrachii to supply the skin on the flexor aspect 

 of the forearm. 



A. AXILLARIS. — The commencement of the axillary artery at the 

 cranial border of the first rib and its course in the axilla have 

 already been examined. It is now found crossing the medial aspect 

 of the shoulder joint obliquely, passing over, in succession, the 

 insertion of the humeral part of the deep pectoral muscle, the 

 coracobrachial muscle, and the insertions of the subscapularis and 

 teres major. On a level with the distal border of the last-named 

 muscle, the axillary artery becomes the brachial. The portion of 

 the vessel at present under examination has the median nerve 

 along its anterior border, and the ulnar nerve running down the 

 opposite border. 



The branches of the axillary are the omocervical trunk, and the 

 external thoracic, thoraco-acromial, subscapular, and anterior circumflex 

 humeral arteries. The first two have been examined in the axilla ; 

 the rest belong to the limb proper. 



A. THORACO-ACROMiALis. — The thoraco-acromial ^ artery leaves the 

 axillary shortly before this vessel arrives at the level of the shoulder 

 joint. Running in a dorsal direction, it supplies branches to the 

 prescapular and humeral parts of the deep pectoral muscle. Another 

 branch enters the cleft between the supraspinous and subscapular 

 muscles to which it furnishes twigs. 



A. SUBSCAPULARIS. — The subscapular artery is by far the largest 



1 Radius [L.], a staff or rod, a spoke of a wheel. 



2 Ulna [L.], wXevYj (olene) [Gr.], the elbow. 



3 Thorax [L.] ; Owpa^ (thorax) [Gr.], the chest ; aKpov (acron) [Gr.], summit or 

 point ; <5jU,os (omos) [Gr.], the shoulder. 



