32 TOPOGRAPHICAL ANATOMY OF THE 



Dissection. — The right ventricle must now be opened. Make an 

 incision through the wall of the ventricle parallel to, and a short 

 distance from, the coronary groove Care must be taken not to insert 

 the knife too deeply, or the tricuspid valve will be injured. The 

 incision should be carried well towards the commencement of the 

 pulmonary artery. A second incision must begin where the first 

 finished, i.e., near the pulmonary artery, and should be made parallel to, 

 and a short distance from, the left longitudinal groove and carried as far 

 as possible towards the apex of the ventricle. 



Ventriculus dexter. — The cavity of the right ventricle ^ has a 

 triangular outline, with the base of the triangle in the vicinity of the 

 right longitudinal groove, while the apex is formed by that part of the 

 ventricle which is known as the conus arteriosus from its conical shape 

 and its communication with the pulmonary artery. During the 

 examination of the exterior of the heart it was noted that the right 

 ventricle does not extend to the apex. This may now be verified. It 

 will be observed that the septum between the two ventricles (septum 

 ventriculorum) is convex towards the right. Thus the cavity of the 

 ventricle would present a crescentic outline were a transverse section 

 to be made. 



The internal surface of the wall of the ventricle, especially where it 

 joins the ventricular septum, is irregular from the presence of fleshy 

 rido-es (trabeculge - carnese) of variable size and form. These are small 

 or absent in the conus arteriosus. Most of the trabeculae are ridges 

 simply ; but one or possibly more (musculi transversi cordis) are cords 

 stretching from the lateral wall of the ventricle to the septum. Three 

 conical muscular processes, the musculi papillares,^ spring from the 

 wall of the ventricle by broad bases, and have fine tendinous cords 

 (chordae tendinese) attached to their apices. 



The opening (ostium atrioventriculare dextrum) from the atrium 

 into the ventricle is guarded by the tricuspid valve (valvula tricus- 

 pidalis) composed of three triangular membranous cusps that hang 

 down into the ventricle. The bases of the cusps are attached to the 

 margin of the atrio-ventricular orifice, and each cusp has chordae 

 tendineae affixed to its ventricular surface and free edge ; the tendinous 

 cords from one papillary muscle being distributed to the adjacent 

 halves of two cusps. It is generally possible to demonstrate smaller 

 cusps between the major cusps. The major cusps have a constant 

 disposition. One lies between the atrio-ventricular opening and the 

 conus arteriosus; another lies against the interventricular septum; 

 while the third is related to the lateral wall of the ventricle. 



' Ventriculus [L.], dim. of venter, the belly; a small cavity. 

 - Trabecula [L.], dim. of trabs, a beam. Carneus [L.], fleshy. 

 ^ Papilla [L.], a nipple. 



