122 CIRCULATION OF THE BLOOD. 



i 



the extent of contraction of the heart and arteries, they are still 

 in a condition to receive an additional quantity of blood forced 

 into them, and that this is far more than is usually reckoned in 

 grains or drops, seems also certain. For if the ventricles become 

 so excessively distended that they will admit no more blood, 

 the heart ceases to beat, (and we have occasional opportunities 

 of observing the fact in our vivisections,) and, continuing tense 

 and resisting, death by asphyxia ensues. 



In the work on the Motion of the Heart and Blood, I have 

 already sufficiently discussed the question as to whether the 

 blood in its motion was attracted, or impelled, or moved by its 

 own inherent nature. I have there also spoken at length of 

 the action and office, of the dilatation and contraction of the 

 heart, and have shown what these truly are, and how the heart 

 contracts during the diastole of the arteries; so that I must hold 

 those who take points for dispute from among them as either not 

 understanding the subject, or as unwilling to look at things for 

 themselves, and to investigate them with their own senses. 1 



For my part, I believe that no other kind of attraction can 

 be demonstrated in the living body save that of the nutriment, 

 which gradually and incessantly passes on to supply the waste 

 that takes place in the tissues ; in the same way as the oil rises 

 in the wick of a lamp to be consumed by the flame. Whence 

 I conclude that the primary and common organ of all sensible 

 attraction and impulsion is of the nature of sinew (nervus), 

 or fibre, or muscle, and this to the end that it may be con- 

 tractile, that contracting it may be shortened, and so either 

 stretch out, draw towards, or propel. But these topics will be 

 better discussed elsewhere, when we speak of the organs of 

 motion in the animal body. 



To those who repudiate the circulation because they neither 

 see the efficient nor final cause of it, and who exclaim, cui bono ? 

 I have yet to reply, having hitherto taken no note of the 

 ground of objection which they take up. And first I own I am 

 of opinion that our first duty is to inquire whether the thing 

 be or not, before asking wherefore it is? for from the facts 

 and circumstances which meet us in the circulation admitted, 

 established, the ends and objects of its institution are especially 



1 Vide Chapter XIV. 



