HEART 8 IMPULSE. 



273 



placed below the diaphragm and the thumb on the antero-supe- 

 rior aspect, the impulse is equally felt by each digit. 



The heart beat communicates its motion to the chest, and this 

 impulse can be seen over a limited area, which varies with the 

 thinness of the individual. This cardiac impulse, as the stroke 

 is called, can be best felt in the fifth intercostal space, a little to 

 the median side of the left nipple. It is found to be synchronous 

 with the ventricular systole. The more important item in caus- 

 ing the impulse is the hardening of the ventricles, while their 

 simultaneous change in shape, from a flattened to a rounded cone, 



FIG. 120. 



Cardiac Tambour, which can be strapped ou to chest wall, so that the central button 

 lies over the heart beat, and the pressure may be regulated by the screws at the side. To 

 the tube bent at right angles is attached the rubber tube which connects the air cavity 

 with that of the writing tambour shown in Fig. 119. 



no doubt, helps to make the sudden tenseness more distinctly felt 

 through the wall of the chest. 



The point at which the impulse is best felt corresponds to the 

 anterior surface of the ventricles some distance above the apex ; 

 it is therefore erroneous to call it the " apex beat." 



Moreover, the motion of the apex is so slight when the wall of 

 the chest is removed, that its " tilting forward " can have no 

 share in causing the impulse : the thoracic wall being always in 

 contact with the apex, it can only move laterally, and cannot 

 hammer against it so as to cause a shock. The " recoil of the 

 ventricles " caused by the blood leaving them, which some think 



