The Heart. 137 



costal cartilage and runs downwards and outwards to the 

 junction of the fifth left rib with its cartilage. Another 

 method of marking the line for this groove is to locate 

 the line for the junctions of the ribs with their cartilages 

 on the left side, then, that portion of it lying 

 between the third and fifth ribs indicates the 

 groove. By means of the landmarks for these two 

 grooves, the four cavities on the anterior surface of the 

 heart may be located thus : The right auricle lies 

 between the line for the auriculo-ventricular groove 

 and those for the right border and the base; the 

 right ventricle, between the line for the auriculo-ventricu- 

 lar groove and the line for the interventricular groove; 

 the left ventricle, between the interventricular groove 

 and the left border of the heart, while the left auricle con- 

 stitutes the remaining part embraced within the general 

 outline of the heart. As seen by these markings, 

 the right ventricle is triangular in shape with its apex up- 

 wards, lies behind the left part of the sternum and the left 

 costal cartilages, and is limited above, i.e., at the apex by the 

 third left cartilage and below by the line for the lower 

 border of the heart, whereas, the left ventricle, viewed an- 

 teriorly, is a long narrow strip forming the left border of 

 the heart. The right appendix auriculae lies behind the 

 junction of the third left cartilage with the sternum, 

 whereas, the left appendix is beneath the third left car- 

 tilage near its junction with the rib, i.e., about one inch 

 from the left border of the sternum. 



Situation of the Valves of the Heart. The pulmonary 

 valves are behind the upper border of the third costal 

 cartilage close to the left margin of the sternum. The 

 aortic lie behind the left margin of the sternum close to 

 the junction of the third cartilage with that bone. The 

 mitral are a little nearer the middle line of the sternum 



