CIRCULATION OF THE BLOOD 91 



the egg immersed in clear tepid water. In the midst of the 

 cloudlet in question there was a bloody point so small that 

 it disappeared during the contraction and escaped the sight, 

 but in the relaxation it reappeared again, red and like the 

 point of a pin; so that betwixt the visible and invisible, 

 betwixt being and not being, as it were, it gave by its pulses 

 a kind of representation of the commencement of life. 



CHAPTER V 

 OF THE MOTION, ACTION AND OFFICE OF THE HEART 



FROM these and other observations of a similar nature, 

 I am persuaded it will be found that the motion of the heart 

 is as follows: 



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 store-house 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 imme- 

 diately sends the blood supplied to it by the auricle into the 

 arteries. The right ventricle sends its charge into the lungs 

 by the vessel which is called vena arteriosa, but which in 

 structure and function, and all other respects, is an artery. 

 The left ventricle sends its charge into the aorta, and 

 through this by the arteries to the body at large. 



These two motions, one of the ventricles, the other 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 anothef, yet all 

 the wheels seem to move simultaneously ; or in that mechani- 

 cal contrivance which is adapted to firearms, where, the 

 trigger being touched, down comes the flint, strikes against 

 the steel, elicits a spark, which falling among the powder, 

 ignites it, when the flame extends, enters the barrel, causes 



