110 WILLIAM HARVEY 



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have one thousand scruples, or about three pounds and a 

 half, of blood injected into the aorta; but the body of neither 

 animal contains above four pounds of blood, a fact which 

 I have myself ascertained in the case of the sheep. 



Upon this supposition, therefore, assumed merely as a 

 ground for reasoning, we see the whole mass of blood 

 passing through the heart, from the veins to the arteries, 

 and in like manner through the lungs. 



But let it be said that this does not take place in half 

 an hour, but in an hour, or even in a day; any way, it 

 is still manifest that more b!ood passes through the heart 

 in consequence of its action, than can either be supplied 

 by the whole of the ingesta, or than can be contained in 

 the veins at the same moment. 



Nor can it be allowed that the heart in contracting 

 sometimes propels and sometimes does not propel, or at 

 most propels but very little, a mere nothing, or an imagi- 

 nary something: all this, indeed, has already been refuted, 

 and is, besides, contrary both to sense and reason. For 

 if it be a necessary effect of the dilatation of the heart 

 that its ventricles become filled with blood, it is equally 

 so that, contracting, these cavities should expel their con- 

 tents; and this not in any trifling measure. For neither 

 are the conduits small, nor the contractions few in num- 

 ber, but frequent, and always in some certain proportion, 

 whether it be a third or a sixth, or an eighth, to the 

 total capacity of the ventricles, so that a like proportion 

 of blood must be expelled, and a like proportion received 

 with each stroke of the heart, the capacity of the ven- 

 tricle contracted always bearing a certain relation to the 

 capacity of the ventricle when dilated. And since, in 

 dilating, the ventricles cannot be supposed to get filled 

 with nothing, or with an imaginary something, so in con- 

 tracting they never expel nothing or aught imaginary, but 

 always a certain something, viz., blood, in proportion to 

 the amount of the contraction. Whence it is to be con- 

 cluded that if at one stroke the heart of man, the ox, or 

 the sheep, ejects but a single drachm of blood and there 

 are one thousand strokes in half an hour, in this interval 

 there will have been ten pounds five ounces expelled; if 





