THE LEFT VENTRICLE. 341 



to the semilunar valves, aorta, and muscular structures 

 of the heart. 



The semilunar valves, three in number, are formed 

 by the reduplication of the endocardium, and consist 

 of three festoons with a central fibre-cartilaginous nodule 

 the corpus Arantii on each. They are much stronger 

 than on the right side. 



The mitral valves guard the auriculo-ventricular 

 orifice. They are triangular leaflets of the endocardium 

 attached to the fibrous ring around the mitral orifice ; 

 they are united by their edges for a short distance, and 



r 



FIG. 146. BASE OF THE HEART, BOTH AURICLES REMOVED. 



rV, right auricle : IV, left anricle : rK, right ventricle : IK, left ventricle : 1, coronary 

 farrow ; 2, right, 3, left auriculo-ventricular ; 4, origin of the aorta ; 5, aortic semilunar 

 valves ; 6, origin of the pulmonary artery ; 7, its semilunar valves ; 8, auricular septum. 



are held in place by the chorda? tendinese. One leaflet is 

 placed between the mitral and aortic orifices ; the other, 

 to the left of the mitral opening. The chordae tendineae 

 are attached as on the right side. 



The columnce carnece are stronger and larger than 

 on the right side, but are disposed in a similar manner. 



The conns arteriosns of each ventricle is the funnel- 

 shaped approach to the pulmonary and aortic openings. 

 These openings are the most constricted part of the 

 conus arteriosns of either ventricle. They are smooth 

 throughout and lined by tightly adherent endocardium. 



