THE INNOMINATE VEIX*. 665 



Surgical Anatomy. There are several points of surgical interest in connection with the 

 axillary vein. Being more superficial, larger, and slightly overlapping the axillary artery, it is 

 more liable to be wounded in the operation of extirpation of the axillary glands, especially as 

 these glands, when diseased, are apt to become adherent to the vessel. When wounded there 

 is always a danger of air being drawn into its interior, and death resulting. This is due not only 

 to the fact that it is near the thorax, and therefore liable to be influenced by the respiratory 

 movements, but also because it is adherent by its anterior surface to the costo-coracoid membrane, 

 and therefore if wounded is likely to remain patulous and favor the chance of air being sucked 

 in. This adhesion of the vein to the fascia prevents its collapsing, and therefore favors the 

 furious bleeding which takes place in these cases. 



To avoid wounding the axillary vein in the extirpation of cancerous glands from the axilla, 

 no sharp cuttinir instruments should be used after the axillary cavity has been freely exposed, 

 and care should be taken to use no undue force in isolating the glands. Should the vein be so 

 imbedded in the malignant deposit that the latter cannot be removed without taking away a part 

 of the vein, this must be done, the vessel having been first ligatured above and below. 



The Subclavian Vein, the continuation of the axillary, extends from the lower 

 border of the first rib to the inner end of the sterno-clavicular articulation, where 

 it unites with the internal jugular to form the innominate vein. It is in relation, 

 in front, with the clavicle and Subclavius muscle ; behind, with the subclavian 

 artery, from which it is separated internally by the Scalenus anticus muscle and 

 phrenic nerve. Below, it rests in a depression on the first rib and upon the pleura. 

 Above, it is covered by the cervical fascia and integument. 



The subclavian vein occasionally rises in the neck to a level with the third part 

 of the subclavian artery, and in two instances has been seen passing with this vessel 

 behind the Scalenus anticus. This vessel is usually provided with valves about 

 an inch from its termination in the innominate, just external to the entrance of the 

 external jugular vein. 



Tributaries. It receives the external and anterior jugular veins and a small 

 branch from the cephalic, outside the Scalenus, and on the inner side of that 

 muscle the internal jugular vein. At the angle of junction with the internal 

 jugular the left subclavian vein receives the thoracic duct, while the right sub- 

 clavian vein receives the right lymphatic duct. 



The Innominate or Brachio-cephalic Veins (Fig. 388) are two large trunks, 

 placed one on each side of the root of the neck, and formed by the union of the 

 internal jugular and subclavian veins of the corresponding side. 



The Right Innominate Vein is a short vessel, an inch in length, which com- 

 mences at the inner end of the clavicle, and. passing almost vertically downward, 

 joins with the left innominate vein just below the cartilage of the first rib, close to 

 the right border of the sternum, to form the superior vena cava. It lies superficial 

 and external to the innominate artery ; on its right side the pleura is interposed 

 between it and the apex of the lung. This vein, at the angle of junction of the 

 internal jugular with the subclavian, receives the right vertebral vein, and, lower 

 down, the right internal mammary, right inferior thyroid, and sometimes the 

 right superior intercostal veins. 



The Left Innominate Vein, about two and a half inches in length, and larger 

 than the right, passes from left to right across the upper and front part of the chest, 

 at the same time inclining downward, to unite with its fellow of the opposite 

 side, forming the *''/" ri.r vena cava. It is in relation, in front, with the first 

 piece of the sternum, from which it is separated by the Sterno-hyoid and Sterno- 

 thyroid muscles, the thynius gland or its remains, and some loose areolar tissue. 

 Behind, it lies across the roots of the three large arteries arising from the arch of 

 the aorta. This vessel is joined by the left vertebral, left internal mammary, left 

 inferior thyroid, and the left superior intercostal veins, and occasionally some thymic 

 and pericardiac veins. There are no valves in the innominate veins. 



Peculiarities. Sometimes the innominate veins open separately into the right auricle ; in 

 such cases the right vein takes the ordinary course of the superior vena cava ; but the left vein, 

 after communicating by a small branch with the right one. passes in front of the root of the left 

 lung. and. turninir to the back of the heart, receives the cardiac veins and terminates in the back 

 of the right auricle. This occasional condition of the veins in the adult is a regular one in the 

 foetus at an early period, and the two vessels are persistent in birds and some mammalia. The 



