Quain's elements of anatomy . al segment of themitral valve ; 7, placed in the interior of the aorta near its commencement andabove its valve ; 7, the exterior of the great aortic sinus ; 8, the tapper part of theconite arteriosus with 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 theaortic arch. most frequently on the right side. In the lower and fore part of theauricle is situated the left amicido-ventricular orifice.
Quain's elements of anatomy . al segment of themitral valve ; 7, placed in the interior of the aorta near its commencement andabove its valve ; 7, the exterior of the great aortic sinus ; 8, the tapper part of theconite arteriosus with 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 theaortic arch. most frequently on the right side. In the lower and fore part of theauricle is situated the left amicido-ventricular orifice. It is of an ovalfoiTQ, and is rather smaller than the corresponding opening between theright auricle and ventricle. On the septum between the auricles, alunated depression may be observed (1), comparable to a mark madeby the finger-nail on a soft surface. This is the vestige of the foramenovale, as it appears on the left side. The depression is limited by asHght crescentic ridge, the concavity of which is turned upwards, and. 488 THE HEART. which is in fact the border of the now adherent membranous valve,which during foetal life is applied to the left side of the then open fora-men ovale. The line of adhesion may vary so as to leave more or less ofa pocket-like recess. The left or posterior ventricle occupies the left border of the heart,but only about a third of its extent appears on the anterior surface, therest being seen behind. It is longer and narrower than the rightventricle, and the cross section of its cavity is oval, not crescentic, theseptum on this side being concave (fig. 424). Its walls, which exceptingnear the apex, are nearly three times as thick as those of the rightventricle, are thickest at the part where the ventricle is widest, aboutone-fourth of its length from the base (fig. 425, 3) ; from tliis pointthey become thinner towards the auricular opening, and still thinner to-wards the apex (o), which is, therefore, the weakest part. The liningmembrane, which
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