48 Motion of the Heart and Blood 



blood percolate the parenchyma of the lungs, than as 

 in other instances chosen a direct and obvious course 

 for I assume that no other path or mode of transit 

 can be entertained. It must be either because the 

 larger and more perfect animals are warmer, and when 

 adult their heat greater ignited, as I might say, and 

 requiring to be damped or mitigated ; therefore it may 

 be that the blood is sent through the lungs, that it may 

 be tempered by the air that is inspired, and prevented 

 from boiling up, and so becoming extinguished, or 

 something else of the sort. But to determine these 

 matters, and explain them satisfactorily, were to enter 

 on a speculation in regard to the office of the lungs and 

 the ends for which they exist; and upon such a subject,, 

 as well as upon what pertains to eventilation, to the 

 necessity and use of the air, &c., as also to the variety 

 and diversity of organs that exist in the bodies of 

 animals in connexion with these matters, although I 

 have made a vast number of observations, still, lest 

 I should be held as wandering too wide of my present 

 purpose, which is the use and motion of the heart, and 

 be charged with speaking of things beside the question,, 

 and rather complicating and quitting than illustrating it ? 

 I shall leave such topics till I can more conveniently 

 set them forth in a treatise apart. And now, returning 

 to my immediate subject, I go on with what yet 

 remains for demonstration, viz. that in the more 

 perfect and warmer adult animals, and man, the blood 

 passes from the right ventricle of the heart by the vena 

 arteriosa, or pulmonary artery, into the lungs, and 

 thence by the arteriae venosae, or pulmonary veins,, into- 

 the left auricle, and thence into the left ventricle of the 

 heart. And, first, I shall show that this may be sOj, 

 and then I shall prove that it is so in fact 



