88« HUMAN ANATOMY. 



pectoral and serratus magnus muscles and in part from the intercostals. They are 

 abundantly supplied with \al\es, and unite to a single stem which presents variations 

 in its connections with the axillary vein similar to those described for the corresponding 

 artery. By means of the costo-axillary veins (vv. costo-axillares ), which pass from 

 the middle portions of the upper six or seven intercostal spaces, it forms anastomoses 

 with the intercostal veins which open into the azygos system. 



These costo-axillary veins open either directly into the long thoracic or into 

 the thoraco-epigastric vein (v. thoraco-epigastrica), a more or less definite stem 

 which extends upward along the lateral walls of the thorax, subcutaneously, to open 

 into the long thoracic near its termination. It receives numerous tributaries from the 

 rich subcutaneous venous net-work which occurs upon the anterior and lateral 

 walls of the thorax (vv. cutaneae pectoris), and communicates directly below with epi- 

 gastric branches from the femoral vein, thus forming an important communication 

 between the superior and inferior caval systems. It also receives the veins coming 

 from the region of the mammary gland, where the pectoral cutaneous veins form a 

 net-work surrounding the nipple, the plexus venosus mammillae. The deeper 

 veins of the gland open in part directly into the long thoracic, whence this has 

 been termed the external mammary vein, and partly into the internal mammary 

 by branches which accompany the perforating branches of the internal mammary 

 artery (page 860). 



Practical Considerations. — When the axillary vein is formed by the junc- 

 tion of the two brachial veins with the basilic vein, the union occurs usually at the 

 inferior border of the subscapularis muscle. The vein is then somewhat shorter 

 than the artery. Occasionally the coalescence of these tributaries does not take 

 place until a level just beneath the lower border of the clavicle has been reached. 

 When this is the case, operations in the axilla will involve the ligation of many com- 

 municating transverse veins crossing the artery to join the venae comites lying upon 

 either side of it. 



Phlebitis of the veins of the upper extremity is but seldom transmitted to the 

 axillary vein, rarely to the subclavian, and never to the internal jugular or innomi- 

 nate (Allen). This immunity is supposed to be due to disproportionately greater 

 size of a main venous trunk as compared with its tributaries ; any of the radicles of 

 the veins of the hand, forearm, and arm — whose calibres are nearly equal — readily 

 transmitting infection. Phlebitis of the axillary vein may, through the costo-axillary 

 branches of the long thoracic vein, extend to within the thorax and result in a septic 

 pleurisy. 



Accidental wounds of the axillary vein — especially of its upper portion — are 

 dangerous on account of its size, its nearness to the thorax — so that it markedly 

 show3 the respiratory Vv'ave — and its attachment to the costo-coracoid membrane, 

 preventing its collapse, favoring hemorrhage, or, when it is empty, permitting the 

 entrance of air. It lies within and a little below the artery, which it overlaps, 

 particularly towards its upper and lower portions, and when it is distended during 

 expiration. As it is straighter than the artery, the curve of the latter carries it a little 

 away from the vein at the middle portion. Abduction of the arm brings the vein to 

 a higher level and often almost in front of the artery so as partly to hide it.. It will 

 therefore be found with this relationship in many operations upon the axilla, and it is 

 on account of it — i.e. , its more superficial position — and of its larger size that the vein is 

 more frequently wounded than is the artery. On the other hand, the axillary artery 

 is oftener ruptured, as in the manipulations for the reduction of old luxations of the 

 shoulder, probably, as such luxations are more frequent in old persons, on account 

 of the greater loss of elasticity of its thicker walls, and possibly on account of greater 

 traction upon it by reason of its deeper and more external position (page 769). 



The close relation of the vein to the deep chain of axillary glands makes it the 

 chief source of danger in operations for the removal of the breast and cleaning out 

 the axilla in cases of mammary cancer, especially if the axillary nodes are already 

 notably involved. It is well, therefore, to expose the vein at an early stage of the 

 operation. If the walls have been invaded by the disease, or if extirpation of the 

 cancerous mass is impossible without resection of the vein, the latter operation may 



