666 



THE VEINS. 



subsequent changes which take place in these vessels are the following : The communicating 

 branch between the two trunks enlarges and forms the future left innominate vein ; the re- 

 maining part of the left trunk is 

 obliterated as i'ar as the heart, 

 where it remains pervious and 

 forms the coronary sinus : a 

 remnant of the obliterated vessel 



-External jugular. is seen in adult life as a fibroiis 



Anterior jugular. 



Superior thyroid. 



Middle thyi 



Mediastinal 1 



and ' , 



pericardiac. p 



band passing along the back of 

 the left auricle and in front of 

 the root of the left lung, called 

 by Mr. Marshall the vestigial 

 fold of the pericardium. 



The internal mammary 

 veins, two in number to 

 each artery, follow the 

 course of that vessel, 

 and receive corresponding 

 branches. The two veins 

 of each side unite into a 

 single trunk, which termi- 

 nates in the corresponding 

 innominate vein. 



The inferior thyroid veins, 

 two, frequently three or 

 four, in number, arise in 

 the venous plexus on the 

 thyroid body, communicat- 

 ing with the middle and 

 superior thyroid veins. The 

 left one descends in front 

 of the trachea behind the 

 Sterno-thyroid muscle, com- 

 municating with its fellow 

 by transverse branches, and 

 terminates in the left in- 

 nominate vein. The right 

 one, which is placed a little 

 to the right of the median 

 line, opens into the right 

 innominate vein just at its 

 junction with the superior 

 vena cava. These veins 

 receive oesophageal, tra- 

 cheal, and inferior laryn- 

 geal veins, and are pro- 

 vided with valves at their 

 termination in the innom- 

 inate veins. 



The Superior Intercos- 

 tal Veins return the blood 

 from the upper intercostal 

 spaces, below the first. 



The rigid superior inter- 

 costal, much smaller than 

 the left, closely corresponds 

 with the superior intercos- 

 tal artery, receiving the 

 blood from the second or second and third intercostal spaces, and, passing do\vn- 



Tntrrna 



FIG. 388 -The venae cavse and azygos veins, with their formative 

 branches. 



