3i8 THE CIRCULATORY SYSTEM. 



the cranial intercostal spaces usually unite two or three 

 together and enter the azygos by one or more common trunks. 

 The azygos also receives bronchial and oesophageal veins, 

 corresponding to the similarly named arteries. 



2. V. mammaria interna (^). — The internal mammary 

 veins follow the corresponding arteries. The two veins unite 

 to form a common trunk which, after receiving a branch from 

 the cranial part of the sternum, enters the vena cava opposite 

 the third rib. 



3. Vv. anonyraae (Fig. 129, ;;/; Fig. 115, /). — The in- 

 nominate veins unite opposite the first intercostal space to form 

 the vena cava superior. Each extends from the cranial end of 

 the vena cava superior craniolaterad to a point a short distance 

 craniad of the first rib and is there formed by the union of the 

 external jugular (Fig. 129, /-) and subclavian (J) veins. The 

 innominate vein has the following branches: 



A and B. Vv. vertebralis and costocervicalis (/). — The 

 vertebral and costocervical veins unite to form a single trunk 

 which enters the innominate about opposite the first rib. 

 These two veins follow the corresponding arteries. (Some- 

 times the vertebral and costocervical veins enter the innominate 

 separately, and in other cases one or more of the components 

 of the costocervical veins (e.g., the transversa colli) may enter 

 the axillary vein. In other cases the entire common trunk of 

 the vertebralis and costocervicalis may enter the superior vena 

 cava directly.) 



C. V. subclavia. — The subclavian vein enters the innom- 

 inate at about the level of the first rib. Outside of the thorax 

 it is called the axillary vein (j) ; this comes from the arm. 



Veins of the Arm.— The blood is returned from the arm 

 by two systems of veins, — a deep and a superficial system. 



The deep system is composed of veins which correspond to 

 the branches of the axillary artery, follow in general the same 

 course, and receive the same names (hig- 122). They unite to 

 form the axillary vein. The brachial vein does not pass with 

 the brachial artery through the supracondyloid foramen. 



The superficial system comprises the vena cephalica and 

 its branches. 



