124 DISSECTION OP THE DOG 



which one disappears into the biceps muscle. The other travels towards the 

 shoulder-joint, and finally anastomoses with the posterior circumflex artery. 



(3) A. circumflexa humeri posterior. — The posterior circumflex humeral 

 artery accompanies the axillary nerve round the back of the proximal part of 

 the humerus. In the dissection of the lateral aspect of the shoulder it will be 

 found under the deltoid muscle. 



(4) A. tJioraco-dorsalis. — Arising close to the commencement of the sub- 

 scapular artery, the thoraco-dorsal artery crosses the medial face of the teres 

 major — to wliich it gives a branch or branches — and ends in the latissimus 

 dorsi and cutaneous muscles and in the skin. 



(5) A. circumflexa scapulae . — The circumflex scapular artery is a small 

 vessel which pierces the origin of the long head of the triceps and ramifies 

 in the infraspinous muscle. From it springs the nutrient artery of the 

 scapula. 



A. BRACHiALis. — From its origin at the distal border of the teres major, the 

 brachial artery runs distalwards in a groove formed by the biceps and the 

 medial head of the triceps. Crossing the flexor aspect of the elbow-joint, it 

 enters the forearm in company mth the median nerve. The musculo-cutaneous 

 nerve follows the oral , and the median nerve the aboral, border of the artery. 



The following branches leave the brachial artery while it is still in the arm : 



(1) A. profunda hrachii. — The deep artery of the arm leaves the brachial 

 close to its origin, and, accompanied by the radial nerve, enters the chink 

 between the long and medial heads of the triceps. 



(2) Ramus muscularis. — A branch to the biceps leaves the brachial in 

 the distal third of the arm. 



(3) A. collateralis ulnaris proximalis. — The proximal ulnar collateral 

 artery takes origin from the aboral side of the brachial almost opposite the 

 artery to the biceps. Crossing the face of the medial head of the triceps in 

 company with the palmar cutaneous ramus of the ulnar nerve, it is expended 

 in the region of the elbow- joint and the ulnar aspect of the proximal half of 

 the forearm. 



(4) A. collateralis radialis proximalis. — The proximal radial collateral 

 artery arises from the brachial about the same level as the origin of the ulnar 

 coUateral, but from the oral border of the parent vessel. After passing in 

 succession over the communicating branch from the musculo-cutaneous to 

 the median nerve, the medial face of the biceps, and the flexor aspect of the 

 elbow, it reaches the forearm. 



(5) A. collateralis radialis distalis. — The distal collateral radial artery 

 leaves the brachial artery close to the elbow-joint. Running lateralwards, 

 almost at right angles to the parent vessel, it lies between the biceps and the 

 brachialis muscles on the one hand and the humerus on the other. The artery 

 thus comes into relationship mth the deep radial nerve, which it accompanies 

 into the forearm. 



