Motion of the Heart and Blood 59 



I have found it to hold upwards of two ounces. Let 

 us assume further, how much less the heart will hold 

 in the contracted than in the dilated state ; and how 

 much blood it will project into the aorta upon each 

 contraction; and all the world allows that with the 

 systole something is always projected, a necessary con- 

 sequence demonstrated in the third chapter, and obvious 

 from the structure of the valves ; and let us suppose as- 

 approaching the truth that the fourth, or fifth, or sixth, 

 or even but the eighth part of its charge is thrown into 

 the artery at each contraction ; this would give either 

 half an ounce, or three drachms, or one drachm of 

 blood as 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. Multi- 

 plying the number of drachms propelled by the number 

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

 or one thousand times three drachms, or a like pro- 

 portional 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 



