206 



THE CIRCULATOKY SYSTEM. 



[CH. XVIII. 



between the right and left auricles which exists in foetal life. 

 The coronary sinus, or the dilated portion of the right coronary 

 vein, also opens into this chamber. 



Fig. 209. 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, i, the two right pul- 

 monary veins cut short ; their openings are seen within the auricle ; i', 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 i' ; 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 camea 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 com- 

 mencement 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.) 



