1898.] 



StStEM OF THE ClFtlUOPTEllA. 



7i 



The Common Carotid Artery on either side runs directly forward, 

 the only thoracic branch being a small offset to the front of the 

 trachea, springing from the artery of the left side close to its 

 origin from the innominate. 



The first branch of the RigM Sahclavian Artery, which here 

 appears like the continuation of the innominate, is the internal 

 mammary, arising from the outer side of the vessel scarcely 1 mm. 

 from the origin of the common carotid. 15 mm. beyond this, 

 from the opposite side of the subclavian, is the origin of the 

 vertebral. This vessel, nearly equal in size to the remainder of 

 the parent trunk, has a short course directly forwards, and 

 then divides into two branches, one running outwards, the 

 other, the vertebral proper, entering the vertebrarterial canal 

 of the sixth cervical vertebra. 



Kg. 7. 



The Internal Mammary Arteries and Veins from the dorsal aspect, X H. — 

 R.I.M. & L.I.M. Eight and Left Internal Mammary Arteries. PS. Pre- 

 sternal Artery. C. Clavicular branch. 1. Ventral Intercostal Artery in 

 first intercostal space ; 2, 2', in second space ; between 1 and 2 lies the 

 second rib, similarly for the rest of the series. 3' is absent on the right 

 side. M.P. Musculo-Pbrenic Artery. S.E. Superior Epigastric Artery. 

 P 1 — P 5. Ventral perforating arteries in the several outer costal spaces. 

 C.M.V. Common Mammary Vein, formed by union of tbe veins of both 

 sides. V.PS. Presternal Vein. A communicating band joins the ventral 

 intercostal veins of the third and fourth spaces on the right side. Except 

 wehre drawn, the veins are exactly similar to the arteries in their distribu- 

 tion, one vein accompanying each artery. 



