446 THE CIRCULATION OF THE BLOOD 



his own distinct declaration as to the considerations 

 which led him to the true theory of the circulation of the 

 blood, and amongst these the valves of the veins are not 

 mentioned. 



Now then we may come to Harvey himself. When you 

 read Harvey's treatise, which is one of the most remarkable 

 scientific monographs with which I am acquainted it 

 occupies between 50 and 60 pages of a small quarto in Latin, 

 and is as terse and concise as it possibly can be when you 

 come to look at Harvey's work, you will find that he had 

 long struggled with the difficulties of the accepted doctrine 

 of the circulation. He had received from Fabricius, and 

 from all the great authorities of the day, the current view 

 of the circulation of the blood. But he was a man with that 

 rarest of all qualities intellectual honesty ; and by dint 

 of cultivating that great faculty, which is more moral than 

 intellectual, it had become impossible for him to say he 

 believed anything which he did not clearly believe. % This is 

 a most uncomfortable peculiarity for it gets you into all 

 sorts of difficulties with all sorts of people but, for scientific 

 purposes, it is absolutely invaluable. Harvey possessed 

 this peculiarity in the highest degree, and so it was impossible 

 for him to accept what all the authorities told him, and he 

 looked into the matter for himself. But he was not hasty. 

 He worked at his new views, and he lectured about them 

 at the College of Physicians for nine years ; he did not print 

 them until he was a man of fifty years of age ; and when he 

 did print them he accompanied them with a demonstration 

 which has never been shaken, and which will stand till the 

 end of time. What Harvey proved, in short, was this (see 

 Fig. 4) that everybody had made a mistake, for want 

 of sufficiently accurate experimentation as to the actual 

 existence of the fact which everybody assumed. To any- 

 body who looks at the blood-vessels with an unprejudiced 

 eye it seems so natural that the blood should all come out 

 of the liver, and be distributed by the veins to the different 

 parts of the body, that nothing can seem simpler or more 

 plain ; and consequently no one could make up his mind 

 to dispute this apparently obvious assumption. But 

 Harvey did dispute it ; and when he came to investigate 

 the matter he discovered that it was a profound mistake, 

 and that, all this time, the blood had been moving in just 

 the opposite direction, namely, from the small ramifications 

 of the veins towards the right side of the heart. Harvey 



