Circulation of the Blood 153 



culation of the blood rises out of it, which, however, 

 has neither been observed nor adduced by any one who 

 has written against me. When we see by the experiment 

 just described, that the systole and diastole of the pulse 

 can be accurately imitated without any escape of fluid, 

 it is obvious that the same thing may take place in the 

 arteries from the stroke of the heart, without the necessity 

 for a circulation, but like Euripus, with a mere motion 

 of the blood alternately backwards and forwards. But 

 we have already satisfactorily replied to this difficulty ; 

 and now we venture to say that the thing could not be 

 so in the arteries of a living animal ; to be assured of 

 this it is enough to see that the right auricle is inces- 

 santly injecting the right ventricle of the heart with 

 blood, the return of which is effectually prevented by 

 the tricuspid valves ; the left auricle in like manner 

 filling the left ventricle, the return of the blood there 

 being opposed by the mitral valves : and then the 

 ventricles in their turn are propelling the blood into 

 either great artery, the reflux in each being prevented 

 by the sigmoid valves in its orifice. Either, conse- 

 quently, the blood must move on incessantly through 

 the lungs, and in like manner within the arteries of the 

 body, or stagnating and pent up, it must rupture the 

 containing vessels, or choke the heart by over disten- 

 sion, as I have shown it to do in the vivisection of a 

 snake, described in my book on the Motion of the 

 Blood. To resolve this doubt I shall relate two 

 experiments among many others, the first of which, 

 indeed, I have already adduced, and which show with 

 singular clearness that the blood flows incessantly and 

 with great force and in ample abundance in the veins 

 towards the heart. The internal jugular vein of a live 

 fallow deer having been exposed, (many of the nobility 

 and his most serene majesty the king, my master, being 

 present,) was divided ; but a few drops of blood were 

 observed to escape from the lower orifice rising up 

 from under the clavicle; whilst from the superior orifice 



