124 Circulation of the Blood 



Were it true that the blood naturally passed from the 

 Ight ventricle of the heart to the lungs, that it might 

 be carried into the left ventricle and from thence into 

 the aorta ; and were the circulation of the blood 

 admitted, who does not see that in affections of the 

 lungs the blood would flow to them in larger quantity 

 and would oppress them, unless it were taken away, 

 first, freely, and then in repeated smaller quantities in 

 order to relieve them, which indeed was the advice of 

 Hippocrates, who, in affections of the lungs takes away 

 blood from every part the head, nose, tongue, arms 

 and feet, in order that its quantity may be diminished 

 and a diversion effected from the lungs ; he takes away 

 blood till the body is almost bloodless. Now admitting 

 the circulation, the lungs are most readily depleted by 

 opening a vein ; but rejecting it, I do not see how any 

 revulsion of the blood can be accomplished by this 

 means ; for did it flow back by the pulmonary artery 

 upon the right ventricle, the sigmoid valves would 

 oppose its entrance, and any escape from the right 

 ventricle into the vena cava is prevented by the 

 tricuspid valves. The blood, therefore, is soon 

 exhausted when a vein is opened in the arm or foot, if 

 we admit the circulation ; and the opinion of Fernelius 

 is at the same time upset by this admission, viz. that in 

 affections of the lungs it is better to bleed from the 

 right than the left arm ; because the blood cannot flow 

 backwards into the vena cava unless the two barriers 

 situated in the heart be first broken down." 



He adds yet further in the same place : l "If the 

 circulation of the blood be admitted, and it be acknow- 

 ledged that this fluid generally passes through the lungs, 

 not through the middle partition of the heart, a double 

 circulation becomes requisite ; one effected through the 

 lungs, in the course of which the blood quitting the 

 right ventricle of the heart passes through the lungs in 

 order that it may arrive at the left ventricle; leaving 



1 Lib. iii, cap. 6. 



