Introduction 15 



divided, as in the brain, the hand, &c., no one could 

 distinguish the arteries from the veins by the dissimilar 

 characters of their coats ; the tunics of both are identical. 

 And then, in an aneurism proceeding from a wounded 

 or eroded artery, the pulsation is precisely the same as- 

 in the other arteries, and yet it has no proper arterial 

 tunic. This the learned Riolanus testifies to, along 

 with me, in his Seventh Book. 



Nor let any one imagine that the uses of the pulse 

 and the respiration are the same, because under the 

 influence of the same causes, such as running, anger, 

 the warm bath, or any other heating thing, as Galen 

 says, they become more frequent and forcible together. 

 For, not only is experience in opposition to this idea, 

 though Galen endeavours to explain it away, when we 

 see that with excessive repletion the pulse beats more 

 forcibly, whilst the respiration is diminished in amount;, 

 but in young persons the pulse is quick, whilst 

 respiration is slow. So is it also in alarm, and amidst 

 care, and under anxiety of mind ; sometimes, too, in 

 fevers, the pulse is rapid, but the respiration is slower 

 than usual. 



These and other objections of the same kind may be 

 urged against the opinions mentioned. Nor are the 

 views that are entertained of the offices and pulse of 

 the heart, perhaps, less bound up with great and most 

 inextricable difficulties. The heart, it is vulgarly said, 

 is the fountain and workshop of the vital spirits, the 

 centre from whence life is dispensed to the several 

 parts of the body ; and yet it is denied that the right 

 ventricle makes spirits ; it is rather held to supply 

 nourishment to the lungs ; whence it is maintained that 

 fishes are without any right ventricle (and indeed every 

 animal wants a right ventricle which is unfurnished 

 with lungs), and that the right ventricle is present 

 solely for the sake of the lungs. 



i, Why, I ask, when we see that the structure of 

 both ventricles is almost identical, there being the same 



