1 6 On the Heart and Blood 



apparatus of fibres, and braces, and valves, and vessels, 

 and auricles, and in both the same infarction of blood, 

 in the subjects of our dissections, of the like black 

 colour, and coagulated why, I say, should their uses 

 be imagined to be different, when the action, motion, 

 and pulse of both are the same ? If the three tricuspid 

 valves placed at the entrance into the right ventricle 

 prove obstacles to the reflux of the blood into the 

 vena cava, and if the three semilunar valves which are 

 situated at the commencement of the pulmonary artery 

 be there, that they may prevent the return of the blood 

 into the ventricle ; wherefore, when we find similar 

 structures in connexion with the left ventricle, should 

 we deny that they are there for the same end, of 

 preventing here the egress, there the regurgitation of 

 the blood ? 



2. And again, when we see that these structures, in 

 point of size, form, and situation, are almost in every 

 respect the same in the left as in the right ventricle, 

 wherefore should it be maintained that things are here 

 arranged in connexion with the egress and regress of 

 spirits, there, i.e. in the right, of blood? The same 

 arrangement cannot be held fitted to favour or impede 

 the motion of blood and of spirits indifferently. 



3. And when we observe that the passages and vessels 

 are severally in relation to one another in point of 

 size, viz., the pulmonary artery to the pulmonary veins ; 

 wherefore should the one be imagined destined to a 

 private or particular purpose, that, to wit, of nourishing 

 the lungs, the other to a public and general function ? 



4. And, as Realdus Columbus says, how can it be 

 conceived that such a quantity of blood should be 

 required for the nutrition of the lungs ; the vessel that 

 leads to them, the vena arteriosa or pulmonary artery 

 being of greater capacity than both the iliac veins ? 



5. And I ask further : as the lungs are so close at 

 hand, and in continual motion, and the vessel that 



: supplies them is of such dimensions, what is the use 



