104 WILLIAM HARVEY 



had not our Maker instituted those supplementary mem- 

 branes." In the eleventh chapter he concludes : " That they 

 (the valves) have all a common use, and that it is to prevent 

 regurgitation or backward motion; each, however, having 

 a proper function, the one set drawing matters from the 

 heart, and preventing their return, the other drawing mat- 

 ters into the heart, and preventing their escape from it. 

 For nature never intended to distress the heart with need- 

 less labour, neither to bring aught into the organ which 

 it had been better to have kept away, nor to take from it 

 again aught which it was requisite should be brought. 

 Since, then, there are four orifices in all, two in either ven- 

 tricle, one of these induces, the other educes." And again 

 he says: "Farther, since there is one vessel, which con- 

 sists of a simple covering implanted in the heart, and 

 another which is double, extending from it (Galen is here 

 speaking of the right side of the heart, but I extend 

 his observations to the left side also), a kind of reser- 

 voir had to be provided, to which both belonging, the 

 blood should be drawn in by one, and sent out by the 

 other." 



Galen adduces this argument for the transit of the blood 

 by the right ventricle from the vena cava into the lungs; 

 but we can use it with still greater propriety, merely 

 changing the terms, for the passage of the blood from the 

 veins through the heart into the arteries. From Galen, 

 however, that great man, that father of physicians, it 

 clearly appears that the blood passes through the lungs from 

 the pulmonary artery into the minute branches of the pul- 

 monary veins, urged to this both by the pulses of the heart 

 and by the motions of the lungs and thorax; that the heart, 

 moreover, is incessantly receiving and expelling the blood 

 by and from its ventricles, as from a magazine or cistern, 

 and for this end it is furnished with four sets of valves, 

 two serving for the induction and two for the eduction of 

 the blood, lest, like the Euripus, it should be incommodiously 

 sent hither and thither, or flow back into the cavity which 

 it should have quitted, or quit the part where its presence 

 was required, and so the heart might be oppressed with 

 labour in vain, and the office of the lungs be interfered 



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