The Heart. 139 



suiting from a defect in their structure, hence, points 

 other than these situations are chosen, at which to apply 

 the stethescope in auscultation, and these are, for the 

 pulmonary valves, at the second left interspace, because 

 the artery lies behind this space and the current of blood 

 conveys the murmur so that it is best heard here. To 

 listen for the sounds of the aortic valves, apply the stethe- 

 scope to the second right interspace (the aorta lying be- 

 hind this space) ; for sounds of the mitral valves, apply it 

 over the apex of the heart, and, for the tricuspid, over the 

 middle of the sternum opposite the fourth interspace, or 

 close to the lower left border of the sternum, i.e., over the 

 right ventricle. A penetrating wound of the third, fourth, 

 fifth or sixth interspace on the right side close to the 

 sternum would enter the right auricle after passing 

 through the integument, superficial and deep fasciae, an- 

 terior intercostal aponeurosis, internal intercostal muscle, 

 internal intercostal fascia, triangularis sterni muscle, sub- 

 pleural tissue, parietal layer of pleura, lung (excepting in 

 the sixth space) covered by the visceral pleura, and, last- 

 ly, the pericardium with the parietal layer of pleura over 

 it. A similarly situated wound, on the left side, would 

 penetrate the same structures as on the right, with the ex- 

 ception of the right auricle (replaced by the right ven- 

 tricle), and of the lung in the lower spaces, since the heart 

 in these spaces is uncovered by the lung. The pleura, 

 also, may escape injury on the left side. 



Clinical Examination of the Heart and 

 Lungs. Heart. The apex of the heart in the adult, 

 is normally situated in the left fifth interspace within the 

 nipple line, but, in the young, it is, as a rule, somewhat 

 higher up, and, in the old, somewhat lower down than 

 this point. The apex may be displaced (1) upwards, 

 when the diaphragm is raised, as in meteorism, ascites, 



