2 THE MECHANISM OF THE CIRCULATION. 



not from the writings of others, I found the task so truly arduous, so 

 full of difficulties, that I was almost tempted to think (with Fracastorius) 

 that the movement of the heart was only to be comprehended by God. 

 For I could neither rightly perceive at first when the systole and when 

 the diastole took place, nor when and where dilatation and contraction 

 occurred, by reason of the rapidity of the movement, which in many 

 animals is accomplished in the twinkling of an eye, coming and going 

 like a flash of lightning ; so that the systole presented itself to me now 

 from this point, now from that the diastole the same ; and then every- 

 thing was reversed, the movements occurring, as it seemed, variously 

 and confusedly together. 1 



" When the heart begins to flag, to move more slowly, and, as it 

 were, to die, the movements then become slower and rarer, the pauses 

 longer, by which it is made much more easy to perceive and unravel 

 what the movements really are, and how they are performed. 



" In the pause," Harvey says, " as in death, the heart is soft, flaccid, 

 exhausted lying, as it were, at rest. In the movement and interval in 

 which this is accomplished, three principal circumstances are to be 

 noted 



" 1. That the heart is erected, and rises upwards to a point, so 

 that at this time it strikes against the breast, and the pulse is felt 

 externally. 



" 2. That it is everywhere contracted, but more especially towards 

 the sides, so that it looks narrower, relatively longer, and more drawn 

 together. 



" 3. The heart being grasped in the hand is felt to become harder 

 during its action. Now, this hardness proceeds from tension ; precisely 

 as when the forearm is grasped its tendons are perceived to become 

 tense and resilient when the fingers are moved. 



"4. It may further be observed in fishes and the colder blooded 

 animals, such as frogs, serpents, etc., that the heart, when it moves, 

 becomes of a paler colour ; when quiescent, of a deeper red colour." 2 



There is also to be noticed in the heart " a certain obscure undulation 

 and lateral inclination in the direction of the axis of the right ventricle, 

 as if twisting itself slightly in performing its work." 3 



Analysing the movements of the chambers of the heart, Harvey 

 determined that " first of all the auricle contracts, and in the course of 

 its contraction forces 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." 



Little can be added to Harvey's admirable description. Turning to 

 a nineteenth-century author Sibson we find the action of the heart 

 described thus : 4 



"The heart, when in action, presents to the eye the most remarkable con- 

 trasts in the size, position, colour, and form of its various cavities and great 



1 Harvey, "An Anatomical Dissertation upon the Movements of the Heart, etc.," ch. i., 

 Canterbury, 1894. 



2 /&^.,ch. ii. 3 7Zm7., ch. v. 



4 "Medical Anatomy," London, 1869, p. 73. 



