To his very dear Friend, DOCTOR ARGENT, the excellent 

 and accomplished President of the Royal College of 

 Physicians, and to other learned Physicians, his most 

 esteemed Colleagues. 



I have already and repeatedly presented you, my learned 

 friends, with my new views of the motion and function of the 

 heart, in my anatomical lectures; hut having now for nine 

 years and more confirmed these views by multiplied demon- 

 strations in your presence, illustrated them by arguments, and 

 freed them from the objections of the most learned and skilful 

 anatomists, I at length yield to the requests, I might say en- 

 treaties, of many, and here present them for general consider- 

 ation in this treatise. 



Were not the work indeed presented through you, my learned 

 friends, I should scarce hope that it could come out scatheless 

 and complete; for you have in general been the faithful wit- 

 nesses of almost all the instances from which I have either 

 collected the truth or confuted error; you have seen my dis- 

 sections, and at my demonstrations of all that I maintain to 

 be objects of sense, you have been accustomed to stand by 

 and bear me out with your testimony. And as this book alone 

 declares the blood to course and revolve by a new route, very 

 different froin the ancient and beaten pathway trodden for so 

 many ages, and illustrated by such a host of learned and dis- 

 tinguished men, I was greatly afraid lest I might be charged 

 with presumption did I lay my work before the public at home, 



