110 APPLIED PHYSIOLOGY 



an hypertrophied heart always displays a strong apex- 

 beat. 



The exact way in which the apex-beat is produced has 

 been much discussed, but everyone is agreed that it does 

 not result from the heart knocking up against the chest 

 wall as the fingers knock on a door, for the simple reason 

 that the heart and chest wall are always in contact. We 

 have seen that the apex-beat is synchronous with the 

 ' compression ' period of the systole, and it is really due 

 to the hardening and change of shape of the heart as it 

 contracts upon its contained ' blood, but before the ex- 

 pulsion of the latter begins. Hence one finds that the 

 apex-beat always precedes the thrill felt over the aortic 

 orifice in aortic stenosis, for the thrill occurs as the blood 

 escapes into the aorta from the ventricles, and thus the 

 apex-beat really occurs before the diminution in size of 

 the ventricle begins, and the old difficulty of explaining 

 how the beat could be felt though the ventricle was 

 getting smaller is seen not to exist. An hypertrophied 

 heart produces a forcible apex-beat, but in dilatation the 

 beat, though diffusely felt, owing to the large surface of 

 heart in contact with the chest wall, is less forcible, 

 because the left ventricle does not completely empty 

 itself, and so the diminution of the volume of the heart 

 during the * expulsion time ' is not so pronounced. 

 There is, then, no necessary relation between the ease 

 with which the apex -beat can be appreciated and the 

 force of the heart; the latter can be judged from the 

 pulse alone. 



It should be noted that when the right ventricle is so 

 much dilated as to bulge into the epigastrium the im- 



