354 



THE AORTA. 



geparation between the two ventricles, where it divides into two branches. 

 The smaller of these continues transversely in the o-roove between the 

 left auricle and ventricle, approaching tlie termination of tlie transverse 

 branch of the left coronary artery ; while the other branch runs longi- 

 tudinally downwards along the posterior wall of the septum between 

 the ventricles, giving branches to each ventricle and to the septum 

 between them. 



In its course the right coronary artery gives, besides tlie offsets 

 already noticed, small branches to the right auricle and ventricle, and 

 also to the first part of the pulmonary artery. Along the right border 

 of the ventricle a rather large branch usually descends towards the apex 

 of the heart, and gives offsets, in its progress, to the anterior and 

 posterior surfaces of the ventricle. 



Fiff. 246. 



Fig. 24C. — View op the Heart and 

 Coronary Arteries from before (R. 

 Quain). J 



The pulmonary artery has been cut short 

 close to its origin in order to show the first 

 part of the aorta. 1, anterior part of the 

 right ventricle ; 2, left ventricle ; 3, root 

 of the pulmonary artery ; 4, ascending part 

 of the arch of the aorta ; 4', the posterior 

 or descending part of the arch ; between 

 these is seen the transverse or middle jiart 

 from which the brachio-cephalic arteries take 

 their origin ; 4", the descending aorta ; 

 5, the appendix and antei'ior part of the 

 right auricle ; 6, those of the left auricle ; 

 7, the right, and 7', the left innominate or 

 brachio-cephalic veins joining to form the 

 vena cava superior ; 8, the inferior vena 

 cava below the diaphragm ; 9, one of the 

 large hepatic veins ; + , placed in the right 

 auriculo-ventricular groove, points to the 

 right or posterior coronary artery ; + + , 

 placed in the anterior interventricular 

 groove, points to the left or anterior coro- 

 nary artery. 



The Irft coronary artery is rather 

 smaller than the preceding, and 

 arises from the left anterior sinus 

 of Valsalva. It passes behind and 

 then to the left side of the pul- 

 monary artery, appearing between 

 that vessel and the left auricular 

 appendage. At first it descends obliquely towards the anterior inter- 

 ventricular sulcus, where it divides into two branches. Of these, one 

 pursues a transverse direction, turning outwards and to the left side 

 in-the groove between the left ventricle and auricle, and approaching 

 at the posterior aspect of the heart the transverse branch of the right 

 coronary artery ; the other branch, much the larger, descends on the 

 anterior surface of the heart along the line of the interventricular 

 groove, to the right of the apex. 



The left coronary artery supplies some small branches at its com- 

 mencement to the pulmonary artery, to the coats of the aorta, and to 



