INTRODUCTION 73 



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 it is 

 also in alarm, and amidst care, and under anxiety of mind ; some- 

 times, 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 which life is dispensed to the several 

 parts of the body. Yet it is denied that the right ventricle makes 

 spirits, which is rather held to supply nourishment to the lungs. 

 For these reasons 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. 



1. Why, I ask, when we see that the structure of both ventricles 

 is almost identical, there being the same apparatus of fibres, and 

 braces, and valves, and vessels, and auricles, and both in the 

 same way in our dissections are found to be filled up with blood 

 similarly black in 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; why, 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, when we have these structures, in points of size, 

 form, and situation, almost in every respect the same in the 

 left as in the right ventricle, why should it be said that things are 

 arranged in the former for the egress and regress of spirits, 



