22 THE METHOD OF MAKING POST-MORTEM EXAMINATIONS. 



line drawn downward from the left nipple. The right boundary extends 

 2.5 cm. to the right of the right edge of the sternum. The portion of the 

 heart uncovered by the lungs is of an irregular quadrangular shape. Its 

 lateral diameter is from 3.8 cm. to 11.1 cm. ; its upper boundary varies 

 from the level of the second costal cartilage to that of the fifth, but it is 

 usually behind the third or fourth cartilage or fourth space. 



The area of the heart which is found uncovered will, however, vary 

 much, according to the degree to which the lungs collapse after opening 

 the chest. Any disease which diminishes the size of the lungs, or pleu- 

 ritic adhesions which retract or bind them down, may increase the area 

 of exposed heart. On the other hand, emphysema, pneumonia, or any 

 disease which increases the size of, or retains the air in, the lungs, may 

 diminish the area of exposed heart. The exposed area varies also with 

 the size of the heart itself. 



The Pericardium is now opened by a slightly oblique incision on its 

 anterior surface. The existence of serous, fibriuous, or purulent exu- 

 date, and of adhesions, is to be noticed. A small quantity of clear serum 

 exists normally in the pericardial sac, and this serum may be blood- 

 stained from beginning decomposition. White thickenings of the peri- 

 cardium on the surfaces of the heart are often seen ; they do not indicate 

 important disease. 



Now that the pericardial sac is open, the position of the heart can be 

 clearly seen. It lies obliquely in the chest, its long axis at an angle of 

 about sixty degrees with that of the thorax. The portion of the heart 

 which is first seen is the anterior surface of the right ventricle ; upward 

 and to the right of this is the right auricle, which lies about two-thirds 

 on the right of the sternum and about one-third behind it. Its upper 

 border usually corresponds to the plane of the middle of the anterior 

 end of the second intercostal space on the right side. Its size varies 

 with the amount of blood which it contains. The left auricle lies behind 

 the root of the pulmonary artery, so that only its appendix is visible. 

 The middle of the auricle corresponds to the third costal cartilage. Of 

 the left ventricle only a narrow rim is seen, on the left side of the right 

 ventricle. The pulmonary valve is usually entirely or in part on the 

 left side of the sternum, behind the second space or third costal cartilage. 



The aortic valve is usually at the level of the third cartilage or the 

 third space, and behind the left two-thirds or half of the sternum. The 

 mitral valve is oblique, the upper end to the left. It is on the level of 

 the third to the fourth cartilage, near the middle of the sternum. Tie 

 tricuspid is oblique, its upper end to the left ; the upper end is at the 

 level of the third cartilage, the third spaee, or the fourth cartilage. 

 The valve is opposite the middle of the sternum. 



The hand should now be passed over the arch of the aorta, to ascer- 

 tain whether or not an aneurism is present. The heart is then grasped 

 at the apex, raised out of the pericardium, tilted upward, and removed 

 unopened by cutting through the vessels at its base. 



To determine the sufficiency of the aortic and pulmonary valves, the 



