THE CHEST. 23 



Dr. Latham years ago in his ' Clinical Lectures.' ' Make a 

 circle of two inches in diameter round a point midway between 

 the nipple and the end of the sternum. This circle will 

 define, sufficiently for all practical purposes, that part of the 

 heart which lies immediately behind the wall of the chest, and 

 is not covered by lung or pleura.' 



Apex of the heart. The apex of the heart pulsates be- 

 tween the fifth and sixth ribs, two inches below the nipple, 

 and one inch to its sternal side. The place and extent, how- 

 ever, of the heart's impulse, vary a little with the position of 

 the body. Of this anyone may convince himself by leaning 

 forwards, backwards, on this side and on that, feeling, at the 

 same time, the heart. Inspiration and expiration also alter 

 the position of the heart. In a deep inspiration it may 

 descend half an inch, and can be felt beating at the pit of the 

 stomach. 



43. Valves of the heart. The aortic valves lie behind 

 the third intercostal space, close to the left side of the 

 sternum. 



The pulmonary valves lie in front of the aortic behind 

 the junction of the third costal cartilage, on the left side, with 

 the sternum. 



The tricuspid valves lie behind the middle of the sternum, 

 about the level of the fourth costal cartilage. 



The mitral valves (the deepest of all) lie behind the third 

 intercostal space, about one inch to the left of the sternum. 



Thus these valves are so situated that the mouth of an 

 ordinary sized stethoscope will cover a portion of them all, if 

 placed over the sternal end of the third intercostal space, on 

 the left side. All are covered by a thin layer of lung ; there- 

 fore we hear their action better when the breathing is for a 

 moment suspended. 



44. Outline of the lung-s. Now let us trace on the chest 

 the outline of the lungs, with as much precision as their ex- 

 pansion and contraction in breathing permit. (See the cut.) 



45. The apex of each lung rises into the neck behind the 

 sternal end of the clavicle and sterno-mastoid muscle as much 

 as an inch and a half: in females rather higher than in males (30). 



