TOPOGEAPHY OF THE HEAET. 



249 



impulses, and the normal impulse may be concealed. For this 

 reason it is more correct in all cases to speak of the visible or 

 palpable thrust as the cardiac impulse than as the apex beat. 

 The outline of the heart projected on the chest wall is as 



pericard. arch of aorta 



sup. ven. cav 



sup 

 ven. cav. 



aortic ; 

 valve i 



aur.-vent./ 

 groove 



tricusp. 

 valve 



pul aorta 



right vent, 

 nipple 



JVsp.4 



s left vent. 



right vent. 



apex of heart 



FIG. 26. THE RELATION OF THE HEART TO THE WALL OF THE THORAX. 

 (Hughes and Keith.} 



follows : The upper border is a line drawn across the sternum 

 at the upper edges of the third costal cartilages ; it extends half 

 an inch beyond the sternum to the right and an inch to the left. 

 The left border, which represents the margo obtusus of the 

 left ventricle, corresponds to a curved line drawn from the left 



