THE HEART. 619 



surrounds this opening. By making one incision along 

 the right side of the heart, and another along the septum 

 cordis, and turning up a flap from below, this cavity will 

 be exposed. Its form is triangular, with the base above 

 and connected with the auricle, while its lower extremity 

 stops a little short of the apex of the heart. The right 

 ventricle occupies the anterior and right side of the heart, 

 and has its walls much thicker than those of the auricle, 

 being estimated about three lines, while the latter is but 

 one line. 



Its interior surface is very irregular from numerous 

 muscular fasciculi called columnce carnece. These fleshy 

 columns are differently arranged ; some are connected 

 along their whole length ; others are fixed by their ex- 

 tremities ; while others again are only attached by one 

 extremity, having the other free, to which is connected 

 several round, tendinous chords called chordae tendinece. 

 These chords interlace among themselves, and are, with 

 the valve, placed between the right ventricle and auricle. 

 This valve is formed by a fold of the lining membrane 

 projecting from the auriculo-ventricular opening, and, 

 from being divided into three pieces, is called tricuspid. 

 One of these pieces is posterior, on the septum cordis ; a 

 second is anterior and the largest, separating the auricu- 

 lar from the pulmonary arterial orifice, while the third is 

 to the right side. This valve prevents the blood, during 

 the contraction of the ventricle, from returning back into 

 the auricle, which is done by the columnar carneae con- 

 tracting, and putting upon the stretch the chordae tendineaa, 

 which draw the several pieces of the tricuspid to each 

 other, while at the same time the blood gets behind, and 

 thus assists to approximate as well as support them, and 

 prevent their being forced open. 



At the superior and left extremity of the right ventricle, 

 is seen the orifice of the pulmonary artery. This orifice is 

 smooth and round, about an inch in diameter, and protected 

 by three valves, termed semilunar or sigmoid. These valves 

 are formed by a duplication of the lining membrane of the 



