HARVEY. 87 



admitting of the passage of blood directly from 

 the right to the left side ; 



(4) That there was no conception of the functions of 

 the heart as the motor power of the movement 

 of the blood, for biologists of that day doubted 

 whether the substance of the heart were really 

 muscular ; they supposed the pulsations to be 

 due to expansion of the spirits it contained \ 

 they believed the only dynamic effect which it 

 had on the blood to be that of sucking it in 

 during its active diastole, and they supposed 

 the chief use of its constant movements to be 

 the due mixture of blood and spirits. 



This was the state of knowledge before Harvey's time. 

 By his great work he established 



(1) That the blood flows continuously in a circuit 



through the whole body, the force propelling it 

 in this unwearied round being the rhythmical 

 contractions of the muscular walls of the 

 heart ; 



(2) That a portion only of the blood is expended in 



nutrition each time that it circulates ; 



(3) That the blood conveyed in the systemic arteries 



communicates heat as well as nourishment 

 throughout the body, instead of exerting a 

 cooling influence, as was vulgarly supposed ; 

 and 



