60 Motion of the 



is still manifest that more blood 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 

 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 

 measure, seeing that neither are the conduits small, 

 nor the contractions 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 of blood must 

 be expelled, and a like proportion received with each 

 stroke of the heart, the capacity of the ventricle con- 

 tracted 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 

 inferred, that if at one stroke the heart in 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 : were there with each stroke two drachms 

 expelled, the quantity would of course amount to twenty 

 .pounds and ten ounces ; were there half an ounce, the 

 quantity would come to forty-one pounds and eight 

 ounces ; and were there one ounce, it would be as much 

 .as eighty-three pounds and four ounces ; the whole of 

 which, in the course of one half-hour, would have been 



