548 



VEINS. 



The inferior thyroid veins, two, frequentl}*- three or four in number, arise 

 in the venous plexus, on the thyroid body, communicating with the mid- 

 dle and superior thyroid 

 Fig. 308. The Venae Cavae and Azygos Veins, 

 with their Formative Branches. 



! Anterior Jugulai* 



Superior Thyroid 



"hIidJ.lt Ttyrti, 



Veins. The left one descends 

 in front of the trachea, be- 

 hind the Sterno-thyroid mus- 

 cles, communicating with its 

 fellow by trans verse branches, 

 and terminates in the left 

 vena innominata. The right 

 one, which is placed a little 

 to the right of the median 

 line, opens into the right 

 vena innominata, just at its 

 junction with the superior 

 cava. These veins receive 

 tracheal and inferior laryn- 

 geal branches, and are pro- 

 vided with valves at their 

 termination in the innominate 

 veins. 



The Superior Intercostal 

 Veins return the blood from 

 the upper intercostal spaces. 



The right superior inter- 

 costal, much smaller than the 

 left, closely corresponds with 

 the superior intercostal ar- 

 tery, receiving the blood from 

 the first, or first and second 

 intercostal spaces, and termi- 

 nates in the right vena in- 

 nominata. Sometimes it 

 passes down, and opens into 

 the vena azygos major. 



The left superior intercostal 

 is always larger than the 

 right, but varies in size in 

 different subjects, being small 

 when the left upper azygos 

 vein is large, and vice versa. 

 It is usually formed by 

 branches from the two or 

 three upper intercostal spaces, 

 and, passing across the arch 

 of the aorta, terminates in 

 the left vena innominata. 

 The left bronchial vein opens 

 into it. 



The Superior Vena Cava 

 receives the blood which is 

 conveyed to the heart from 

 the whole of the upper half 

 of the body. It is a short 

 trunk, varying from two 

 inches and a half to three 



