190 CIRCULATORY SYSTEM. 



meter, resembling strongly the corresponding orifice of the 

 right side of the heart. 



The left Ventricle (Ventriculus Sinister, posterior) in the 

 shape of its cavity resembles a long ovoidal or conical body. 

 Its parietes are generally three times as thick as those of the 

 right ventricle, amounting to about eight lines: it is thicker, 

 however, at its inferior tTian at its superior part, as it gradually 

 decreases in approaching the aorta. 



Its internal surface is arranged on the same principle with 

 that of the right ventricle, being roughened by the presence of 

 numerous fleshy columns (Columnce Carnece] some of which 

 are connected with the valvular apparatus between it and the 

 left auricle: others form an intricate reticular texture on its 

 sides, and a few pass from one side to the other. As this sur- 

 face approaches the orifice of the aorta, it becomes smooth, 

 so that no impediment may be afforded to the passage of the 

 blood. 



The Ostium Venosum, on the side of this cavity, has its mar- 

 gin looking tendinous, and furnished with a duplicature of the 

 lining membrane that surrounds it. This duplication, by being 

 severed on its loose edge into two divisions, obtains the name 

 of Mitral Valve, '(Valvula Mitralis.) Its margin is secured 

 from being pushed into the left auricle by numerous chordse 

 tendineae, which are attached by their other extremities to four 

 or five columnar carneae projecting from the surface of the ven- 

 tricle. The whole internal arrangement of this cavity indicates 

 a great increase of strength over that of the right side : in the 

 robustness of its fleshy columns, the number and size of its ten- 

 dinous chords, and the greater thickness of its valve. The 

 upper division of the mitral valve is placed immediately below 

 the orifice of the aorta, and is considerably broader than the 

 other, so that when it opens to admit blood, it is in some mea- 

 sure thrown over the aortic orifice. There is less of an in- 

 tertexture among the tendinous chords here than on the right 

 side of the heart : they cluster more, and, owing to the breadth 

 of the extremities of the fleshy columns, are more parallel. 



The Septum of the Ventricles is of considerable thickness, 



