io8 Motion of the Heart and Blood 



and the walls of which are thinner, as in fishes, 

 serpents, birds, and very many genera of animals, in 

 all of them the arteries differ little or nothing in the 

 thickness of their coats from the veins. 



Farther, the reason why the lungs have such ample 

 vessels, both arteries and veins, (for the capacity of the 

 pulmonary veins exceeds that of both the crural and 

 jugular vessels,) and why they contain so large a 

 quantity of blood, as by experience and ocular in- 

 spection we know they do, admonished of the fact 

 indeed by Aristotle, and not led into error by the 

 appearances found in animals which have been bled 

 to death, is, because the blood has its fountain, and 

 storehouse, and the workshop of its last perfection in 

 the heart and lungs. Why, in the same way we find in 

 the course of our anatomical dissections the arteria 

 venosa and left ventricle so full of blood, of the same 

 black colour and clotted character, too, as that with 

 which the right ventricle and pulmonary artery are filled, 

 inasmuch as the blood is incessantly passing from one 

 side of the heart to the other through the lungs. 

 Wherefore, in fine, the pulmonary artery or vena 

 arteriosa has the constitution of an artery, and the 

 pulmonary veins or arteriae venosae have the structure 

 of veins ; because, in sooth, in function and constitu- 

 tion, and everything else, the first is an artery, the 

 others are veins, in opposition to what is commonly 

 believed ; and why the pulmonary artery has so large 

 an orifice, because it transports much more blood than 

 is requisite for the nutrition of the lungs. 



All these appearances, and many others, to be noted 

 in the course of dissection, if rightly weighed, seem 

 clearly to illustrate and fully to confirm the truth con- 

 tended for throughout these pages, and at the same 

 time to stand in opposition to the vulgar opinion ; for 

 it would be very difficult to explain in any other way to 

 what purpose all is constructed and arranged as we 

 have seen it to be. 



