MOTION OF THE HEART AND BLOOD 



wise two auricles. On the other hand, in some animals 

 there is an auricle without a ventricle, or anyway a 

 sac like an auricle, or the vein itself, dilated in one 

 place, pulsates. This is seen in hornets, bees, and 

 other insects, in experiments on which I think I can 

 show not only a pulse but also a respiration in that 

 part called a tail. This can be seen to lengthen and 

 contract, sometimes quickly, sometimes slowly, as 

 the insect seems to be blown up and to need more air. 

 But more of this in the Treatise on Respiration.^ 



Likewise it is clear that the auricles beat, contract, 

 and, as I said before, push blood into the ventricles. 

 So wherever there is a ventricle, an auricle is needed. 

 Not alone, as commonly believed, to be a receptacle 

 and store-house for blood. For what use is a pulsation 

 in retaining? The auricles exist as the initial motive 

 power of the blood. Especially the right auricle, the 

 first to live and the last to die, as said before. They 

 are necessary in order to cast the blood conveniently 

 into the ventricles. These, continually contracting, 

 throw out more fully and forcibly the blood already 

 in motion, just as a ball-player can send a ball harder 

 and farther by striking it on a rebound than if he 

 simply throws it. Moreover, contrary to common 

 opinion, neither the heart nor anything else can draw 

 anything into itself by dilating or distending, unless 

 like a sponge previously compressed, while it is return- 



^ If the Treatise on Respiration was written, it was probably 

 destroyed by the Parliamentary soldiers who sacked Harvey's rooms 

 in Whitehall in 1642, when Harvey was with Charles I at Edgehill. 



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