CH. XVIII.] 



THE HEART 



209 



appendix is the only part of the auricle seen from the front, and 

 corresponds with that on the right side, but is thicker, and the 



FIG. 218. The left auricle and ventricle opened and a part of their anterior and left walls removed. . 

 The pulmonary artery has been divided at its commencement ; the opening into the left ventricle 

 is carried a short distance into the aorta between two of the segments of the semilunar valves ; and 

 the left part of the auricle with its appendix has been removed. The right auricle is out of view. 

 1, the two right pulmonary veins cut short ; their openings are seen within the auricle ; 1', placed 

 within the cavity of the auricle on the left side of the septum and on the part which forms the 

 remains of the valve of the foramen ovale, of which the crescentic fold is seen towards the left hand 

 of 1' ; 2, a narrow portion of the wall of the auricle and ventricle preserved round the auriculo- 

 ventricular orifice ; 3, 3', the cut surface of the walls of the ventricle, seen to become very much 

 thinner towards 3", at the apex ; 4, a small part of the anterior wall of the left ventricle which has 

 been preserved with the principal anterior columna carnea or musculus papillaris attached to it ; 

 5, 5, musculi papillares ; 5', the left side of the septum, between the two ventricles, within the 

 cavity of the left ventricle; 6, 6', the mitral valve ; 7, placed in the interior of the aorta, near its 

 commencement and above the three segments of its semilunar valve which are hanging loosely 

 together; 7', the exterior of the great aortic sinus; 8, the root of the pulmonary artery and its 

 semilunar valves ; 8', the separated portion of the pulmonary artery remaining attached to the 

 aorta by 9, the cord of the ductus arteriosus ; 10, the arteries rising from the summit of the aortic 

 arch. (Allen Thomson.) 



interior is smoother. The left auricle is only slightly thicker than 

 the right. The left auriculo-ventricular orifice is oval, and a little 



O 



