ON THE MOTION 



OF THE HEART AND BLOOD 



IN ANIMALS 



CHAPTER I 

 THE AUTHOR'S MOTIVES FOR WRITING 



WHEN I first gave my mind to vivisections, as a 

 means of discovering the motions and uses of the 

 heart, and sought to discover these from actual 

 inspection, and 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 motion 

 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 

 motion, which in many animals is accomplished in the twink- 

 ling 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 everything 

 was reversed, the motions occurring, as it seemed, variously 

 and confusedly together. My mind was therefore greatly 

 unsettled nor did I know what I should myself conclude, nor 

 what believe from others. I was not surprised that Andreas 

 Laurentius should have written that the motion of the heart 

 was as perplexing as the flux and reflux of Euripus had 

 appeared to Aristotle. 



At length, by using greater and daily diligence and investi- 

 gation, making frequent inspection of many and various 

 animals, and collating numerous observations, I thought that 

 I had attained to the truth, that I should extricate myself 



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