666 ANGIOLOGY 





lower down, the right internal mammary and right inferior thyroid veins, and some- 

 times the vein from the first intercostal space. 



The Left Innominate Vein (v. anonyma sinistra), about 6 cm. in length, begins 

 behind the sternal end of the clavicle and runs obliquely downward and to the 

 right behind the upper half of the manubrium sterni to the sternal end of the first 

 right costal cartilage, where it unites with the right innominate vein to form the 

 superior vena cava. It is separated from the manubrium sterni by the Sterno- 

 hyoideus and Sternothyreoideus, the thymus or its remains, and some loose areolar 

 tissue. Behind it are the three large arteries, innominate, left common carotid, and 

 left subclavian, arising from the aortic arch, together with the vagus and phrenic 

 nerves. The left innominate vein may occupy a higher level, crossing the jugular 

 notch and lying directly in front of the trachea. 



Tributaries. Its tributaries are the left vertebral, left internal mammary, left 

 inferior thyroid, and the left highest intercostal veins, and occasionally some 

 thymic and pericardiac veins. 



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

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

 left superior vena cava, as it is then termed which may communicate by a small branch with 

 the right one, passes in front of the root of the left lung, and, turning to the back of the heart, 

 ends in the right atrium. This occasional condition in the adult is due to the persistence of the 

 early fetal condition, and is the normal state of things in birds and some mammalia. 



The internal mammary veins (w. mammarice internee) are venae comitantes 

 to the lower half of the internal mammary artery, and receive tributaries corre- 

 sponding to the branches of the artery. They then unite to form a single trunk, 

 which runs up on the medial side of the artery and ends in the corresponding 

 innominate vein. The superior phrenic vein, i. e., the vein accompanying the peri- 

 cardiacophrenic artery, usually opens into the internal mammary vein. 



The inferior thyroid veins (w. thyreoidece inferiores) two, frequently three or 

 four, in number, arise in the venous plexus on the thyroid gland, communicating 

 with the middle and superior thyroid veins. They form a plexus in front of the 

 trachea, behind the Sternothyreoidei. From this plexus, a left vein descends and 

 joins the left innominate trunk, and a right vein passes obliquely downward and to 

 the right across the innominate artery to open into the right innominate vein, 

 just at its junction with the superior vena cava; sometimes the right and left veins 

 open by a common trunk in the latter situation. These veins receive esophageal 

 tracheal, and inferior laryngeal veins, and are provided with valves at their 

 terminations in the innominate veins. 



The highest intercostal vein (v. intercostalis suprema; superior intercostal veins) 

 (right and left) drain the blood from the upper three or four intercostal spaces. 

 The right vein (v. intercostalis suprema dexlra) passes downward and opens into the 

 vena azygos; the left vein (v. intercostalis suprema sinistra) runs across the arch 

 of the aorta and the origins of the left subclavian and left common carotid 

 arteries and opens into the left innominate vein. It usually receives the left 

 bronchial vein, and sometimes the left superior phrenic vein, and communicates 

 below with the accessory hemiazygos vein. 



The superior vena cava (v. cava superior) drains the blood from the upper half 

 of the body. It measures about 7 cm. in length, and is formed by the junction of 

 the two innominate veins. It begins immediately below the cartilage of the right 

 first rib close to the sternum, and, descending vertically behind the first and second 

 intercostal spaces, ends in the upper part of the right atrium opposite the upper 

 border of the third right costal cartilage : the lower half of the vessel is within the 

 pericardium. In its course it describes a slight curve, the convexity of which is 

 to the right side. 



