280 THE CIRCULATION. 



William Harvey, again, gives a better account of this part of the 

 heart's action than has been published by any subsequent writer. 

 The following exceedingly graphic and appropriate description, 

 taken from his book, shows that he derived his knowledge, not 

 from any secondary or hypothetical sources, but from direct and 

 careful study of the phenomena in the living animal. 



"First of all," he says, 1 "the auricle contracts, and in the course 

 of its contraction throws the blood (which it contains in ample 

 quantity as the head of the veins, the storehouse and cistern of the 

 blood) into the ventricle, which being filled, the heart raises itself 

 straightway, makes all its fibres tense, contracts the ventricles, and 

 performs a beat, by which beat it immediately sends the blood 

 supplied to it by the auricle, into the arteries ; the right ventricle 

 sending its charge into the lungs by the vessel which is called vena 

 arteriosa, but which, in structure and function, and all things else, 

 is an artery ; the left' ventricle sending its charge into the aorta, 

 and through this by the arteries to the body at large. 



" These two motions, one of the ventricles, another of the auricles, 

 take place consecutively, but in such a manner that there is a kind 

 of harmony or rhythm preserved between them, the two concurring 

 in such wise that but one motion is apparent, especially in the 

 warmer blooded animals, in which the movements in question are 

 rapid. Nor is this for any other reason than it is in a piece of 

 machinery, in which, though one wheel gives motion to another, 

 yet all the wheels seem tQ move simultaneously; or in that 

 mechanical contrivance which is adapted to fire-arms, where the 

 trigger' being touched, down comes the flint, strikes against the 

 steel, elicits a spark, which falling among the powder, it is ignited, 

 upon which the flame extends, enters the barrel, causes the explo- 

 sion, propels the ball, and the mark is attained ; all of which inci- 

 dents, by reason of the celerity with which they happen, seem to 

 take place in the twinkling of an eye." 



The above description indicates precisely the manner in which 

 the contraction of the ventricle follows successively and yet con- 

 tinuously upon that of the auricle. The entire action of the auricles 

 and ventricles during a pulsation is accordingly as follows : The 

 contraction begins, as we have already stated, at the auricle. 

 Thence it runs immediately forward to the apex of the heart. The 

 entire ventricle contracts vigorously, its walls harden, its apex 



1 Op. cit., p. 31. 



