DISSECTION OF THE DOG 123 



N. mediantjs.— At its origin the median nerve is closely connected with 

 the ulnar and radial nerves. All three accompany the axillary and brachial 

 arteries as far as the origin of the deep artery of the arm where the radial 

 nerve leaves the other two. The median and ulnar continue onwards in 

 company with each other and the brachial artery as far as about the junction 

 of the middle and distal thirds of the arm, where the ulnar parts company 

 with the median nerve and the artery. The median nerve accompanies the 

 artery into the forearm. 



N. radialis. — The radial nerve is generally the largest of the branches of the 

 brachial plexus. As previously stated, it accompanies the median and ulnar 

 nerves for some distance. At the distal border of the teres major the nerve 

 sinks into the interval between the long and medial heads of the triceps. 



N. ulnaris. — The ulnar is as large as, or possibly larger than, the 

 median nerve, by the side of which it runs as far as beyond the middle of the 

 arm. Coursing, from this point, along the face of the medial head of the 

 triceps, it passes into the forearm under cover of the antibrachial fascia. 



In the distal third of the arm the ulnar nerve contributes a palmar cutaneous 

 branch (ramus cutaneus palmaris), which reaches the forearm by first running 

 obliquely between the medial head of the triceps and the tensor of the anti- 

 brachial fascia, and then across the medial face of the olecranon of the ulna. 



A. axillaris. — The mode of origin and some of the branches of the axillary 

 artery have been examined during the dissection of the axilla. The further 

 course of the artery is first across the medial aspect of the shoulder-joint, and 

 then over the coraco-brachial muscle and the tendon of insertion of the teres 

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

 artery becomes the brachial. 



The only branch which belongs properly to the limb is the subscapular 

 artery. 



A. suBSCAPULARis. — The subscapular artery is the largest branch of the 

 axillary ; indeed it is larger than the continuation of the parent trunk, a circum- 

 stance which has led to the conception that the axillary artery terminates at 

 this point by bifurcation. 



The subscapular artery passes along the axillary border of the scapula 

 between the subscapular and teres major muscles and on the medial face of the 

 origin of the long head of the triceps. The full course of the vessel cannot be 

 followed without reflection of the teres major ; but this dissection had better 

 be postponed for a little. 



The following vessels are branches of the subscapular artery : 



(1) Branches (rami musculares) to the subscapular, teres major, trapezius, 

 deltoid, supraspinous, and brachio-cephalic muscles. 



(2) A. circumflexa humeri anterior. — In many cases the anterior circumflex 

 humeral artery arises directly from the axillary. Crossing the surface of the 

 coraco-brachial (or teres major) muscle, the artery divides into two twigs, of 



