THE LEFT VENTRICLE. 



ovale. The line of adhesion may vary so as to leave more or less of a pocket-like 

 ess. 

 The left ventricle occupies the left border of the heart, but only about a third 



recess. 



Fig. 312. THE LEFT AURICLE AND VENTRICLE 



OPENED AND A PART OF THE WALL RE- 

 MOVED SO AS TO SHOW THEIR INTERIOR. 



(Allen Thomson.) \ 



The commencement of the pulmonary ar- 

 tery has been cut away, so as to show the 

 aorta ; the opening into the left ventricle 

 has been carried a short distance into the 

 aorta between two of the semilunar flaps ; 

 and part of the auricle with its appendix 

 has been removed. 1, right pulmonary veins 

 cut short ; 1', placed within the cavity of the 

 auricle on the left side of the septum, on 

 the part formed by the valve of the foramen 

 ovale, of which the crescentic border is seen ; 

 2', a narrow portion of the wall of the auricle 

 and ventricle preserved around the auriculo- 

 ventricular orifice ; 3, 3', cut surface of the 

 wall of the ventricle, seen to become very 

 much thinner towards 3", at the apex ; 4, a 

 small part of the wall of the left ventricle 

 which has been preserved with the left pa- 

 pillary muscle attached to it ; 5, 5, right 

 papillary muscles ; 5', the left side of the 

 septum ventriculorum ; 6, the anterior or 

 aortic segment, and 6', the posterior or pa- 

 rietal segment of the mitral valve ; 7, placed 

 in the interior of the aorta near its com- 

 mencement and above its valve ; 7', the ex- 

 terior of the great aortic sinus ; 8, the upper 

 part of the conus arteriosus with the root 

 of the pulmonary artery and its valve ; 8', 

 the separated portion of the pulmonary trunk 

 remaining attached to the aorta by 9, the 

 cord of the ductus arteriosus ; 10, the 

 arteries arising from the aortic arch. 



Fig. 313. VIEW OF THE BASE OF THE VEN- 

 TRICULAR PART OF THE HEART, SHOW- 

 ING THE RELATIVE POSITION OF THE 

 ARTERIAL AND AURICULO-VENTRICULAR 



ORIFICES. (Allen Thomson.) f 



The muscular fibres of the ventricles are 

 exposed by the removal of the pericardium, 

 fat, blood-vessels, &c. ; the pulmonary artery 

 and aorta and the auricles have been re- 

 moved ; the valves are in the closed con- 

 dition. 1, 1, right ventricle ; 1', conus 

 arteriosus ; 2, 2, left ventricle ; 3, 3, the 

 divided wall of the right auricle ; 4, that 

 of the left ; 5, the infundibular ; 5', the 

 right, and 5" the septal segment of the tri- 

 cuspid valve ; 6, the anterior or aortic, 

 and 6', the posterior or parietal segment 

 of the mitral valve (in the angles between 

 these segments are seen smaller lobes) ; 7, 

 the pulmonary artery ; ^8, placed upon the root of the aorta ; 9, the right, 9' ; the left coronary artery. 



of its extent appears on the anterior surface, the rest being seen behind. It is 

 longer and narrower than the right ventricle, and the cross section of its cavity is 

 oval, not crescentic, the septum on this side being concave (fig. 311). Its wall, 



