HARVEY'S WORK 63 



confirm that the blood passes through lungs and heart by 

 the force of the ventricles, and is driven thence and sent 

 forth to all parts of the body. There it makes its way into 

 the veins and pores of the flesh. It flows by the veins 

 everywhere from the circumference to the centre, from 

 the lesser to the greater veins, and by them is discharged 

 into the vena cava and finally into the right auricle of the 

 heart. [The blood is sent] in such a quantity, in one 

 direction, by the arteries, in the other direction by the 

 veins, as cannot possibly be supplied by the ingested 

 food. ... It is therefore necessary to conclude that the 

 blood in the animals is impelled in a circle, and is in a 

 state of ceaseless movement ; that this is the act or func- 

 tion of the heart, which it performs by means of its pulse ; 

 and that it is the sole and only end of the movement and 

 pulse of the heart." 



We have now come to an end of Harvey's discovery, 

 and have let him tell of it, as far as possible, in his own 

 words. We have seen how the power of words, words 

 such as innate heat, spirits, and anastomosis, had their 

 influence in helping or retarding the course of knowledge. 

 Words at different ages have different meanings, and at 

 any age the exact and precise meaning of a word is often 

 difficult to define. Often, however, much hangs on the 

 exact interpretation of a scientific term. Science is, of 

 course, concerned with observations and with inferences 

 from them, not with words about them. But our know- 

 ledge of observations and inferences can only be expressed 

 in words. Scientific nomenclature, therefore, though of 

 secondary importance, must not be despised. Harvey's 

 discovery introduced a very striking change into physio- 

 logical nomenclature, a change to which we have often 

 referred in the pages of this work. 



In the old physiology the arteries were considered as 



