444 ANGIOLOGY. 



The Vena azygos is a long single branch, whose radicles- 

 originate near the first lumbar vertubra. It passes forwards on 

 the right side of the postarior aorta, below the bodies of the 

 dorsal vertebrae, reaching the sixth, where it becomes inclined 

 downwards, and terminates in the anterior vena cava. It receives 

 branches from the spinal and psoe muscles, the posterior thirteen 

 right, and usually the posterior five or six left intercostal, and 

 also the oesophageal veins. 



_ ,_^ iiRACHlAL VEIN. 



vFiG- 167. a, I.) 



The brachial vein, the largest trunk which enters into the 

 formation of the anterior vena cava, receives the greater part of 

 the blood from the anterior extremity, as well as extrinsic 

 branches corresponding to those of the artery, and the sub- 

 cutaneous thoracic or spur vein. 



The Pedal plexuses and digital veins are identical with those 

 of the posterior limb. 



The Metacaepal veins are the external, internal, and inter- 

 osseous. The internal vein, by far the largest, passes up the 

 limb to the side of the flexor tendons, in company with the artery 

 and nerve, the vein being in front, the artery in the centre ; 

 passing the knee in compan}'^ with the i;^dio-palmar artery it is 

 continued as the internal subcutaneous vein. It forms a free 

 anastomosis with other metacarpal veins, receiving also branches 

 from the joint. The external metacarpal is situated on the 

 external side of the flexor tendons, accompanied hy the corre- 

 sponding nerve, and it also receives branches from the skin 

 and adjacent structures. On reaching the upper part of the 

 trapezium, it divides into numerous branches, which either anas- 

 tomose with those of the internal, or go to form the posterior radial 

 and cubital veins. The deep or interosseous vein is very irregular 

 and flexuous, and may be double ; it passes up the limb between 

 the posterior surface of the cannon bone and the suspensory liga- 

 ment. At the head of the metacarpus, it splits up to unite with 

 branches of the external and internal veins, and sends one or two 

 small branches, through the carpal sheath, which help to form 

 the posterior radial vein. 



The Posterior radial vein is a continuation of the meta- 

 carpals, terminating at the lower end of the humerus in the 



