HEART AND BLOOD. 49 



propelled by the heart at each pulse into the aorta; which 

 quantity, by reason of the valves at the root of the vessel, can 

 by no means return into the ventricle. Now in the course of 

 half an hour, the heart will have made more than one thousand 

 beats, in some as many as two, three, and even four thousand. 

 Multiplying the number of drachms propelled by the number 

 of pulses, we shall have either one thousand half ounces, or one 

 thousand times three drachms, dr a like proportional quantity of 

 blood, according to the amount which we assume as propelled 

 with each stroke of the heart, sent from this organ into the 

 artery ; a larger quantity in every case than is contained in the 

 whole body! In the same way, in the sheep or dog, say that 

 but a single scruple of blood passes with each stroke of the 

 heart, in one half hour we should 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 blood passes through the heart in conse- 

 quence 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 some- 

 times propels and sometimes does not propel, or at most propels 

 but very little, a mere nothing, or an imaginary 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 contents ; and this not in any trifling mea- 

 sure, seeing that neither are the conduits small, nor the con- 

 tractions few in number, 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 



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