THE BE AC RIAL OE AXIL LAST AETEEIES. 565 



3. Muscular branches, which escape at intervals during the course of the 

 vessel, and are sent forwards and backwards. The anterior pass either to the 

 internal or external side of the scapula, or to both sides of that bone, whose 

 posterior border they embrace in their bifurcation. The internal divisions 

 creep in the fissures on the deep face of the bone, throwing their ramuscules 

 into the subscapularis muscle, and even reaching the super- (antea-J spinatus, 

 as well as the insertion of the angularis and great serratus muscles. The 

 external divisions traverse the large extensor of the fore-arm, to be dis- 

 tributed to the super- and subspinati and the abductor muscles of the arm, 

 one furnishing the nutrient artery of the scapula. The postericr branches 

 supply the abductor of the arm, and the large extensor of the fore-arm. 



HUMERAL ARTERY, OR TERMINAL ARTERY OF THE BRACHIAL TRUNK. 



(Fig. 347, A.) 



Course. This, a continuation of the axillary artery, which changes its 

 name after giving off the subscapular branch, at first describes a slight 

 curve forwards to descend almost vertically within the thoracic limb by 

 crossing obliquely the direction of the humerus, and terminates above the 

 inferior extremity of that bone by two branches which constitute the anterior 

 and posterior radial arteries. 



Relations. In its course, the humeral artery corresponds : in front, to 

 the median or ulno-plantar nerve, and to the posterior border of the coraco- 

 humeralis muscle, which it closely follows ; behind, to the vein of the arm, 

 and through it to the ulnar nerve ; outwardly, to the common tendon of the 

 great dorsal muscle and the adductor muscle of the arm, to the middle 

 extensor of the fore-arm, and to the humerus ; inwardly, to the sheath of the 

 coraco-radialis muscle, which separates the pectoralis magnus from the 

 artery of the arm, and in which this vessel is inclosed, in common with its 

 satellite vein, the lymphatic glands and vessels of the arm, as well as with 

 the nerves of the fore-limb. 



Collateral branches. Among these may be distinguished four, which 

 merit particular mention. They are the prehumeral, external and int> rnal 

 collateral arteries of the elbow, and the principal artery of the coraco-radialis 

 muscle. We need only indicate, besides these, several irregular ramuscules 

 which go to the latter muscle, to the coraco-humeralis, and to the middle 

 extensor of the fore-arm. 



1. Prehumeral, or anterior circumflex artery of the shoulder. This 

 arises at a right angle, is directed forward, passes between the two branches 

 of the coraco-humeralis, turns round the anterior face of the humerus, 

 beneath the bicipital groove, and terminates in the mastoido-humeralis 

 muscle. During its progess it gives off branches to the scapulo-brachial 

 and biceps muscles, as well as to the articulation of the shoulder. Among 

 the articular ramifications, there is one which ascends outwardly on the 

 tendon of the subspinatus, and whose ultimate divisions anastomose with the 

 ramuscules of the posterior circumflex artery. 



2. Deep humeral, or external collateral artery of the elbow. A very large 

 branch which emerges from the humeral trunk, by forming with that artery 

 an almost right angle at the common terminal tendon of the great dorsal 

 muscle and the adductor of the arm. After a very short course, it divides 

 into two principal branches; one of these sends its ramuscules into the 

 body of the large extensor muscle ; the other passes under that muscle in 



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