442 ARTERIES. 



wards to the right side, in the groove between the right auricle and ventricle, 

 and curving around the right border of the heart, runs along its posterior sur- 

 face as far as the posterior interventricular groove, where it divides into two 

 branches, one of which continues onwards in the groove between the left auricle 

 and ventricle, and anastomoses with the left coronary ; the other descends 

 along the posterior interventricular furrow, supplying branches to both ven- 

 tricles and to the septum, and anastomosing at the apex of the heart with the 

 descending branch of the left coronary. 



This vessel sends a large branch -along the thin margin of the right ventricle 

 to the apex, and numerous small branches to the right auricle and ventricle, 

 and the commencement of the pulmonary artery. 



The Left Coronary, smaller than the former, arises immediately above the free 

 edge of the left semilunar valve, a little higher than the right ; it passes for- 

 wards between the pulmonary artery and the left appendix auriculae, and descends 

 obliquely towards the anterior interventricular groove, where it divides into 

 two branches. Of these, one passes transversely outwards in the left auriculo- 

 ventricular groove, and winds around the left border of the heart to its poste- 

 rior surface, where it anastomoses with the superior branch of the right coro- 

 nary ; the other descends along the anterior interventricular groove to the 

 apex of the heart, where it anastomoses with the descending branch of the right 

 coronary. The left coronary supplies the left auricle and its appendix, both 

 ventricles, and numerous small branches to the pulmonary artery, and com- 

 mencement of the aorta. 



Pecidiarities. These vessels occasionally arise by a common trunk, or their number may be 

 increased to three ; the additional branch being of small size. More rarely, there are two additional 

 branches. 



ARTERIA INNOMINATA. 



The Innominate Artery is the largest branch given off from the arch of the 

 aorta. It arises from the commencement of the transverse portion in front of 

 the left carotid, and, ascending obliquely to the upper border of the right 

 sterno-clavicular articulation, divides into the right carotid and subclavian 

 arteries. This vessel varies from an inch and a half to two inches in length. 



Relations. In front, it is separated from the first bone of the sternum by the 

 Sterno-hyoid and Sterno-thyroid muscles, the remains of the thymus gland, 

 and by the left innominate and right inferior thyroid veins which cross its root. 

 Behind, it lies upon the trachea, which it crosses obliquely. On the right side 

 is the right vena innominata, right pneumogastric nerve, and the pleura ; and 

 on the left side, the remains of the thymus gland, and origin of the left carotid 

 artery. 



PLAN OF THE RELATIONS OF THE INNOMINATE ARTERY. 



In front. 

 Sternum. 



Sterno-hyoid and Sterno-thyroid muscles. 

 Remains of thymus gland. 

 I.H't innominate and inferior thyroid veins. 

 Inferior cervical cardiac branch from right pneumogastric nerve. 



Right side. f \ Left ff - fji , 



Right vena Innominate. / lnnomlnate \ BeafcinTS thvmus. 



Uiirht pneumogustric nerve. I Artery. I Left carotid " 



J'k'ura. \ / 



Behind. 

 Trachea. 



Peculiarities in point of (ttviximi. \Vhon the bifurcation of the innominate artery varies from 

 the point above mentioned, it sometimes ascends a considerable distance above the sternal end of 



