THE CIRCULATION OF THE BLOOD 435 



type, and about one-seventh of the thickness, you would 

 have the sum total of the printed matter which Harvey 

 contributed to our literature. And yet in that sum total 

 was contained, I may say, the materials of two revolutions 

 in as many of the main branches of biological science. If 

 Harvey's published labours can be condensed into so small 

 a compass, you must recollect that it is not because he did 

 not do a great deal more. We know very well that he did 

 accumulate a very considerable number of observations on 

 the most varied topics of medicine, surgery, and natural 

 history. But, as I mentioned to you just now, Harvey, 

 for a time, took the royal side in the domestic quarrel of the 

 Great Rebellion, as it is called ; and the Parliament, not 

 unnaturally resenting that action of his, sent soldiers to 

 seize his papers. And while I imagine they found nothing 

 treasonable among those papers, yet, in the process of 

 rummaging through them, they destroyed all the materials 

 which Harvey had spent a laborious life in accumulating ; 

 and hence it is that the man's work and labours are re- 

 presented by so little in apparent bulk. 



What I chiefly propose to do to-night is to lay before you 

 an account of the nature of the discovery which Harvey 

 made, and which is termed the Discovery of the Circulation 

 of the Blood. And I desire also, with some particularity, 

 to draw your attention to the methods by which that dis- 

 covery was achieved ; for, in both these respects, I think, 

 there will be much matter for profitable reflection. 



Let me point out to you, in the first place, with respect to 

 this important matter of the movements of the heart and 

 the course of the blood in the body, that there is a certain 

 amount of knowledge which must have been obtained with- 

 out men taking the trouble to seek it knowledge which 

 must have been taken in, in the course of time, by every- 

 body who followed the trade of a butcher, and still more so 

 by those people who, in ancient times, professed to divine 

 the course of future events from the entrails of animals. 

 It is quite obvious to all, from ordinary accidents, that the 

 bodies of all the higher animals contain a hot red fluid 

 the blood. Everybody can see upon the surface of some 

 part of the skin, underneath that skin, pulsating tubes, 

 which we know as the arteries. Everybody can see 

 under the surface of the skin more delicate and softer 

 looking tubes, which do not pulsate, which are of a bluish 

 colour, and are termed the veins. And every person who 



