1907.J 



AZYGOS VEINS IN MAMMALS. 



187 



Its affluents, however, commence on the posterior side of the fourth 

 rib Beyond the last pair of affluents, which lie behind the 

 thirteenth (and last) rib, the trunk is continued back as a veiy 

 slender vessel. The first intercostal artery which crosses this 

 azygos lies behind the tenth rib. Anteriorly, the second and 

 third intercostal spaces give rise to vessels which unite into a 

 trunk which debouches into the left subclavian vein, ihe rignt 



Azygos veins of Gasella euchore. Lettering as in text-fig. 62. 



subclavian, it may be remarked, joins the precava quite a con- 

 siderable distance behind the opening of the left subclavian— a 

 marked asymmetry which is not common. It receives, however, 

 no branches from intercostal spaces and enters the thoracic cavity 

 in the usual position— that is, in front of the first rib. The right 

 azyo-os is of fair size ; it enters the precava about opposite the 

 fourth rib. It receives branches from intercostal spaces 2 to 6 

 (inclusive). 



