THE ANTERIOR VENA CAVA. 697 



where it is directed forwards in following the superior border of the posterior 

 superficial pectoral muscle, accompanied by an arterial ramuscule and a thick 

 nerve. It insinuates itself beneath the olecranian muscles, and finally terminates 

 in the humeral vein by joining the branch that follows the deep muscular artery. 



4. Deep Veins of the Forearm. 



A. Anterior Radial Vein. — This follows the same track, and affects the 

 same variations, as the corresponding artery. 



B. Posterior Radial Veins. — The posterior radial artery is always accom- 

 panied, and, as it were, enveloped, by a fasciculus of three or four venous 

 branches, which frequently anastomose with each other, and are reinforced by 

 collateral branches, among which the interosseous vein must be noted. 



These radial branches commence above the carpus, by continuing the meta- 

 carpal veins. They concur to form the humeral vein, in joining the other 

 antibrachial veins at the inferior extremity of the arm. 



C. Ulnar Vein. — This vessel is lodged, with the nerve and small artery of 

 the same name, in the interspace between the oblique and internal flexors of the 

 metacarpus. A number of muscular and subcutaneous branches enter this vein. 



It has the same origin as the posterior radial veins. Its superior or terminal 

 extremity bends forward, close to the trunk of the ulnar artery, and goes to the 

 inferior extremity of the humeral vein. Frequently the ulnar vein is double in 

 the latter portion of its track, and between these two branches lies the artery. 

 It always communicates at this point, by one or more branches, with the deep 

 muscular vein. 



5. Superficial Veins of the Forearm. 



Placed outside the fibrous sheath formed by the antibrachial aponeourosis, 

 these veins, which are principally two in numlber, are maintained against the 

 external face of that membrane by a thin fascia that separates them from the 

 skin. 



A. Median or Internal Subcutaneous Vein (Fig. 389, 31). — This is 

 also one of the vessels selected for the operation of phlebotomy. It is the 

 continuation of the internal metacarpal vein, ascends from the inner face of the 

 carpus to the superior extremity of the forearm, by crossing the radius in a very 

 oblique manner, and terminates in two very large branches, the posterior of 

 which is the basilic vein, and the anterior the cephalic vein. 



The basilic vein traverses the superficial pectoral muscle, to aid in forming 

 the humeral trunk (Fig. 389, 34). 



The cephalic, or plate vein, crosses the superficial band of the biceps muscle, is 

 lodged in the space comprised between the mastoido-humeralis and anterior 

 superficial pectoral muscles, and afterwards opens in the jugular vein (Fig. 

 389, 35). 



B. External Subcutaneous or Anterior Radial Vein (Fig. 389, 32). 

 — Less considerable than the preceding, this vein arises at the carpal region, in 

 its course occupies the anterior face of the forearm, and terminates in uniting its 

 superior extremity either to the internal subcutaneous, or the cephalic vein ; the 

 last is most frequently the case. 



