650 p-i THE ARTERIES. 



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

 and posterior radial arteries. 



Relations. — In its course, the humeral artery is related : 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 latissimus dorsi and 

 the teres major, to the caput parvum, and to the humerus ; inwardly, to the 

 sheath of the biceps muscle, which separates the posterior deep pectoral from the 

 artery of the arm, and in which this vessel is enclosed, 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 prelmmeral, external and internal collateral 

 arteries of the elboiv, and the principal artery of the flexor brachii muscle. "We 

 need only indicate, besides these, several irregular ramuscules which go to the 

 latter muscle, to the coraco-humeralis, and to the caput parvum. 



1. Prehwmral, or anterior circumflex artery (Fig. 376, 4). — 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 progress it 

 gives off branches to the coraco-humeralis 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 infra-spinatus ; the ultimate 

 divisions anastomose with the ramuscules of the posterior circumflex artery. 



2. Deep humeral (humeralis profunda), or ext&rnal collateral artery of the 

 elbow (Fig. 376, 5). — 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 latissimus dorsi and the teres major. After a very short 

 course, it divides into two principal branches ; one of these sends its ramuscules 

 into the caput magnum and medium ; the other passes under that muscle in 

 turning round the humeralis obliquus, along with the radial nerve, and reaching 

 beneath the caput medium, descends — still with its satelhte nerve — in front of 

 the articulation of the elbow, where this branch anastomoses with the anterior 

 radial artery. It supplies all the olecranian muscles — except the caput magnum — 

 as well as the humeralis obliquus and the extensor metacarpi magnus. 



3. Epicondyloid, internal collateral of the elbow {cubital), or ulnar artery (Fig. 

 376, 7). — Smaller than the external collateral, this artery arises at the nutrient fora- 

 men of the humerus, and proceeds backwards on the internal face of that bone, to 

 pass beneath the caput magnum, by following in a more or less flexuous manner 

 the inferior border of the caput parvum ; it then descends, at first behind the 

 epicondyle, then on the forearm, which it passes along for its whole length, 

 underneath the aponeurotic sheath of this region, between the flexor metacarpi 

 medius and externus, accompanied by the ulnar vein and nerve of the same 

 name, and the tendon of the ulnar portion of the perforans muscle. Arriving 

 near the carpus, this long branch anastomoses by inosculation with a branch from 

 the posterior radial artery. 



In its antibrachial course, this artery only gives off very attenuated branches, 

 the study of which is of little importance. But before attaining the forearm, it 

 furnishes : 1. The nutrient artery of the humerus. 2. Articular ramuscules. 

 3. More or less voluminous muscular branches, particularly for the caput 



