356 



THE HEART. 



the auricular and the ventricular portions ; and on the ventricular portion two 

 longitudinal interventricular furrows, situated one on the anterior, the other on the 

 posterior surface, mark its division into a right and left chamber. They extend 

 from the base of the ventricular portion, and are continuous one with the other a 

 little to the right of the apex, which is thus formed entirely by the wall of the left 

 ventricle. The anterior interventricular furrow (fig. 306, + +) is nearer to the left, 

 and the posterior furrow (fig. 308) nearer to the right side of the heart, the right 

 ventricle forming more of the anterior, and the left more of the posterior surface 

 of the organ. In the furrows run the coronary arteries and veins with the lym- 

 phatic vessels and nerves, embedded in fatty tissue and covered by the visceral 

 layer of the pericardium. 



CAVITIES OP THE HEART. 



The heart, as before remarked, contains four chambers or compartments, a right 

 and a left auricle and a right and a left ventricle. 



The right auricle (fig. 306, 5) is best brought into view on turning the heart 

 somewhat to the left side ; it is then seen to occupy the right and anterior portion 



Fig. 309. INTERIOR OP THE RIGHT AU- 

 RICLE AND VENTRICLE, EXPOSED BY 

 REMOVAL OF THE GREATER PART OF 

 THEIR RIGHT AND ANTERIOR WALLS. 



(Allen Thomson. ) \ 



1, superior vena cava ; 2, inferior 

 vena cava ; 2', hepatic veins ; 3, septum 

 of the auricles ; 3', fossa ovalis, the Eus- 

 tachian valve is just below ; 3", aperture 

 of the coronary sinus with its valve ; 

 + , + , right auriculo-ventricular groove, 

 a narrow portion of the adjacent walls 

 of the auricle and ventricle having been 

 preserved ; 4, 4, on the septum, the 

 cavity of the right ventricle ; 4', large 

 anterior papillary muscle ; 5, infundibu- 

 lar, 5', right, and 5", posterior or septal 

 segment of the tricuspid valve ; 6, pul- 

 monary artery, a part of the anterior wall 

 of that vessel having been removed, and 

 a narrow portion of it preserved at ifcs 

 commencement where the pulmonary 

 valve is attached ; 7, the aortic arch close 

 to the cord of the ductus arteriosus ; 8, 

 ascending aorta covered at its commence- 

 ment by the auricular appendix and pul- 

 monary artery ; 9, placed between the 

 innominate and left common carotid ar- 

 teries ; 10, appendix of the left auricle ; 

 11, 11, left ventricle. 



of the base of the organ. When 

 thus viewed the auricle appears 

 of a quadrangular form, the 



superior and inferior venae cavae occupying respectively the upper and lower 

 posterior angles, while a tongue-shaped portion, the auricular appendix or auricle 

 irroper, 1 is seen to project from the anterior and upper angle and to turn to the 

 left over the root of the aorta. The main part of the auricle, that into which 

 the great veins directly pour their blood, is commonly named sinus venosus or 

 atrium, to distinguish it from the auricular appendix. At the outer and posterior 



1 So termed from its resemblance to the external ear of some animals. 



