290 Mayow 



OF THE PULSATION OF THE HEART 



As to the contraction of the heart, the distmguished 

 Dr Lower has given such an accurate description of 

 its motion, as also of its structure, that it is scarcely 

 possible to add anything to it. That the heart is 

 really a muscle, and that the contraction of its fibres 

 diminishes the space of its ventricles and drives out 

 the blood, is quite indubitable. But here we come 

 across a by no means small difficulty : for seeing that 

 the heart is contracted and becomes smaller in its 

 systole, how is it that at that very time it strikes 

 the left side of the chest ? For it would seem that 

 in its contraction the heart should rather move in- 

 wards and further f^om the wall of the chest. 



Hence some have supposed that it is not the heart 

 but the great artery, distended with blood, which 

 strikes the chest. But in fact the great artery, soon 

 after its origin, turns backwards towards the spine^ 

 so that its pulsation could not be felt outside. Nor 

 can we say that the auricles of the heart in their 

 contraction strike the thorax, because they, just like 

 the heart, become smaller in their systole, and 

 besides, their deeper position is less suitable for 

 striking the chest. 



And lastly, we cannot believe that the apex of the 

 heart impinges on and strikes the thorax, because of 

 its vibration and jump ; for I have found from 

 vivisections that the pulsation of the heart is produced 

 by its ventricles swelling up into a tumour : in fact, if 

 the thorax of a dog be quickly opened, and a finger, 

 or the hand, be placed on the left ventricle of the 

 heart, you will feel the ventricle swell up with a jump 

 and strongly strike the hand or the finger placed on 



