WILLIAM HARVEY. 



393 



lungs, to the left ventricle, was in no wise an an- 

 ticipation of the discovery of the circulation of 

 the blood. For the blood which traverses this 

 part of its course no more describes a circle than 

 the dweller in a street who goes out of his own 

 house and enters his next-door neighbor's does so. 

 Although there may be nothing but a party-wall 

 between him and the room he has just left, it 

 constitutes an efficient defense de circuler. Thus, 

 whatever they may have known of the so-called 

 pulmonary circulation, to say that Servetus, or 

 Columbus, or Caesalpinus, deserves any share of 

 the credit which attaches to Harvey, appears to 

 me to be to mistake the question at issue. 



It must further be borne in mind, that the de- 

 termination of the true course taken by the whole 

 mass of the blood is only the most conspicuous 

 of the discoveries of Harvey; and that his analy- 

 sis of the mechanism by which the circulation is 

 brought about is far in advance of anything 

 which had previously been published. For the 

 first time, it is shown that the walls of the heart 

 are active only during its systole or contraction, 

 and that the dilatation of the heart, in the dias- 

 tole, is purely passive. Whence it follows, that 

 the impulse by which the blood is propelled is a 

 vis a lergo, and that the blood is not drawn into 

 the heart by any such inhalent or suctorial action 

 as not only the predecessors but many of the 

 successors of Harvey imagined it to possess. 



Harvey is no less original in his view of the 

 cause of the arterial pulse. In contravention of 

 Galen and of all other anatomists up to his own 

 time, he affirms that the stretching of the arteries 

 which gives rise to the pulse is not due to the 

 active dilatation of their walls, but to their pas- 

 sive distention by the blood which is forced into 

 them at each beat of the heart ; reversing Galen's 

 dictum, he says that they dilate as bags and not 

 as bellows. This point of fundamental, practical 

 as well as theoretical, importance is most admi- 

 rably demonstrated, not only by experiment, but 

 by pathological illustrations. 



One of the weightiest arguments in Harvey's 

 demonstration of the circulation is based upon 

 the comparison of the quantity of blood driven 

 out of the heart, at each beat, with the total 

 quantity of blood in the body. This, so far as I 

 know, is the first time that quantitative consid- 

 erations are taken into account in the discussion 

 of a physiological problem. But one of the most 

 striking differences between ancient and modern 

 physiological science, and one of the chief reasons 

 of the rapid progress of physiology in the last 

 half - century, lies in the introduction of exact 



quantitative determinations into physiological ex- 

 perimentation and observation. The moderns 

 use means of accurate measurement, which their 

 forefathers neither possessed nor could conceive, 

 inasmuch as they are products of mechanical 

 skill of the last hundred years, and of the advance 

 of branches of science which hardly existed, even 

 in germ, in the seventeenth century. 



Having attained to a knowledge of the circu- 

 lation of the blood, and of the conditions on which 

 its motion depends, Harvey had a ready deductive 

 solution for problems which had puzzled the older 

 physiologists. Thus the true significance of the 

 valves in the veins became at once apparent. Of 

 no importance while the blood is flowing in its 

 normal course toward the heart, they at once op- 

 pose any accidental reversal of its current, which 

 may arise from the pressure of adjacent muscles, 

 or the like. And, in like manner, the swelling 

 of the veins on the farther side of the ligature, 

 which so much troubled Cassalpinus, became at 

 once intelligible, as the natural result of the dam- 

 ming up of the returning current. 



In addition to the great positive results which 

 are contained in the treatise which Harvey mod- 

 estly calls an " Exercise " — and which is, in truth, 

 not so long as many a pamphlet about some 

 wholly insignificant affair — its pages are charac- 

 terized by such precision and simplicity of state- 

 ment, such force of reasoning, and such a clear 

 comprehension of the methods of inquiry and of 

 the logic of physical science, that it holds a unique 

 rank among physiological monographs. Under 

 this aspect, I think I may fairly say that it has 

 rarely been equaled and never surpassed. 



Such being the state of knowledge among his 

 contemporaries, and such the immense progress 

 effected by Harvey, it is not wonderful that the 

 publication of the "Exercitatio " produced a pro- 

 found sensation. And the best indirect evidence 

 of the originality of its author, and of the revolu- 

 tionary character of his views, is to be found in 

 the multiplicity and the virulence of the attacks 

 to which they were at once subjected. 



Eiolan, of Faris, had the greatest reputation 

 of any anatomist of those days, and he followed 

 the course which is usually adopted by the men 

 of temporary notoriety toward those of enduring 

 fame. According to Riolan, Harvey's theory of 

 the circulation was not true ; and, besides that, it 

 was not new; and, furthermore, he invented a 

 mongrel doctrine of his own, composed of the old 

 views with as much of Harvey's as it was safe 

 to borrow, and tried therewith to fish credit for 



