THE HEAKT. 329 



which commences at the auricle, is immediately propagated to the ven- 

 tricle, and runs rapidly from the base of the heart to its apex, very 

 much in the manner of a peristaltic motion, excepting that it is more 

 sudden and vigorous. This part of the heart's action is described by 

 Harvey in very graphic terms, evidently drawn from direct study of the 

 phenomena in the living animal. 



" First of all," he says, "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, b}' 

 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 to 

 move simultaneous^ ; 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 explosion, propels the ball, and the mark is attained ; all of 

 which incidents, 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 continuously 

 upon that of the auricle. The contraction begins, as already stated, at 

 the auricle. Thence it runs immediately forward to the apex of the 

 heaVt. The entire ventricle contracts vigorously, its walls harden, its 

 apex protrudes, strikes against the walls of the chest, and twists from 

 left to right, the auriculo-ventricular valves shut back, the first sound 

 is produced, and the blood is driven into the aorta and pulmonary artery. 

 These phenomena occupy about one-half the time of pulsation. Then 

 the ventricle is relaxed, and a short period of repose ensues. During 

 this period the blood flows from the large veins into the auricle, and 

 through the auriculo-ventricular orifice into the ventricle; filling the 

 ventricle, by a kind of passive dilatation, about two-thirds or three- 

 quarters full. Then the auricle contracts with a quick motion, forces 

 the last drop of blood into the ventricle, distending it to its full capa- 

 22 



