26 Motion of the 



apex, which is felt externally by its striking against the 

 chest, the thickening of its parietes, and the forcible 

 expulsion of the blood it contains by the constriction of 

 its ventricles. 



Hence the very opposite of the opinions commonly 

 received, appears to be true ; inasmuch as it is generally 

 believed that when the heart strikes the breast and the 

 pulse is felt without, the heart is dilated in its ventricles 

 and is filled with blood ; but the contrary of this is the 

 fact, and the heart, when it contracts [and the shock is 

 given], is emptied. Whence the motion which is 

 generally regarded as the diastole of the heart, is in 

 truth its systole. And in like manner the intrinsic 

 motion of the heart is not the diastole but the systole ; 

 neither is it in the diastole that the heart grows firm 

 and tense, but in the systole, for then only, when tense, 

 is it moved and made vigorous. 



Neither is it by any means to be allowed that the 

 heart only moves in the line of its straight fibres, 

 although the great Vesalius, giving this notion counten- 

 ance, quotes a bundle of osiers bound into a pyramidal 

 heap in illustration ; meaning, that as the apex is ap- 

 proached to the base, so are the sides made to bulge 

 out in the fashion of arches, the cavities to dilate, the 

 ventricles to acquire the form of a cupping-glass and so 

 to suck in the blood. But the true effect of every one 

 of its fibres is to constringe the heart at the same time 

 that they render it tense ; and this rather with the effect 

 of thickening and amplifying the walls and substance of 

 the organ than enlarging its ventricles. And, again, as 

 the fibres run from the apex to the base, and draw the 

 apex towards the base, they do not tend to make the 

 walls of the heart bulge out in circles, but rather 

 the contrary ; inasmuch as every fibre that is circularly 

 disposed, tends to become straight when it contracts ; 

 and is distended laterally and thickened, as in the case 

 of muscular fibres in general, when they contract, that is, 

 when they are shortened longitudinally, as we see them 



