HEART AND BLOOD. 23 



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 countenance, quotes a bundle of 

 osiers bound into a pyramidal heap in illustration; meaning, that 

 as the apex is approached 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 ampli- 

 fying 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 in the bellies of the muscles of the 

 body at large. To all this let it be added, that not only are 

 the ventricles contracted in virtue of the direction and con- 

 densation of their walls, but farther, that those fibres, or bands, 

 styled nerves by Aristotle, which are so conspicuous in the ven- 

 tricles of the larger animals, and contain all the straight fibres, 

 (the parietes of the heart containing only circular ones,) when 

 they contract simultaneously, by an admirable adjustment all 

 the internal surfaces are drawn together, as if with cords, and 

 so is the charge of blood expelled with force. 



Neither is it true, as vulgarly believed, that the heart by 

 any dilatation or motion of its own, has the power of drawing 

 the blood into the ventricles ; for when it acts and becomes 

 tense, the blood is expelled; when it relaxes and sinks toge- 

 ther it receives the blood in the manner and wise which will 

 by and by be explained. 



