534 THE BLOOD-VASCULAR SYSTEM. 



inner head of the Triceps, next upon the insertion of the Coraco-brachialis, and 

 lastly on the Brachialis anticus ; by its outer side, it is in relation with the com- 

 mencement of the median nerve and the Coraco-brachialis and Biceps muscles, 

 which overlap the artery to a considerable extent; by its inner side, its upper 

 half is in relation with the internal cutaneous and ulnar nerves, its lower half with 

 the median nerve. The basilic vein lies on the inner side of the artery, but is sepa- 

 rated from it in the lower part of the arm by the deep fascia. It is accompanied by 

 two venae comites, which lie in close contact with the artery, being connected 

 together at intervals by short transverse communicating branches. 



PLAN OF THE RELATIONS OF THE BRACHIAL ARTERY. 



In front. 



Integument and fasciae. 



Bicipital fascia, median basilic vein. 



Median nerve. 



Overlapped by Coraco-brachialis and Biceps. 



Outer side. / Inner side. 



Median nerve (above). Artery. Internal cutaneous and Ulnar nerves. 



Coraco-brachialis. \ Median nerve (below). 



Biceps. Basilic vein. 



Behind. 



Triceps (long and inner heads). 

 Musculo-spiral nerve. 

 Superior profunda artery. 

 Coraco-brachialis. 

 Brachialis anticus. 



SURGICAL ANATOMY OF THE BEND OF THE ELBOW. 



At the bend of the elbow the brachial artery sinks deeply into a triangular 

 interval, the base of which is directed upward, and may be represented by a line 

 connecting the two condyles of the humerus ; the sides are bounded, externally, by 

 the inner edge of the Supinator longus ; internally, by the outer margin of the 

 Pronator radii teres ; its floor is formed by the Brachialis anticus and Supinator 

 brevis. This space contains the brachial artery with its accompanying veins, the 

 radial and ulnar arteries, the median and musculo-spiral nerves, and the tendon of 

 the Biceps. The brachial artery occupies the middle line of this space, and 

 divides opposite the neck of the radius into the radial and ulnar arteries ; it is 

 covered, in front, by the integument, the superficial fascia, and the median basilic 

 vein, the vein being separated from direct contact with the artery by the bicipital 

 fascia. Behind, it lies on the Brachialis anticus, which separates it from the 

 elbow-joint. The median. nerve lies on the inner side of the artery, close to it 

 above, but separated from it below by the coronoid origin of the Pronator radii 

 teres. The tendon of the Biceps lies to the outer side of the space, and the mus- 

 culo-spiral nerve still more externally, situated upon the Supinator brevis and 

 partly concealed by the Supinator longus. 



Peculiarities of the Brachial Artery as regards its Course. The brachial artery, ac- 

 companied by tbe median nerve, may leave the inner border of the Biceps and descend toward 

 the inner condyle of the humerus, where it usually curves round a prominence of bone, the 

 supra-condylar process, from which a fibrous arch is usually thrown over the artery ; it then 

 inclines outward, beneath or through the substance of the Pronator radii teres muscle, to the 

 bend of the elbow. The variation bears considerable analogy to the normal condition of the 

 artery in some of the carnivora : it has been referred to in the description of the humerus 

 (page 146). 



As regards its Division. Occasionally, the artery is divided for a short distance at its 

 upper part into two trunks, which are united above and below. A similar peculiarity occurs 

 in the main vessel of the lower limb. 



