,^Y* ^— <K<^ 

 •'library ' 



( 315 ) 



ceed the fmaller in the velocity of its alcent towards the furface. 

 And as this is the cafe with air bubbles in their afcent, the fame 

 will hold good in falling bodies of equal denfity, as in balls of dif- 

 ferent fizes, difcharged with equal force from cannon. 



But to return to the fubjcdt, I drew out the pillon very flowly, and 

 having obferved the whole with the greateft attention I was able, I 

 found that the air produced in the fmall tube from C towards D, 

 by the operation, amounted to a feven hundred and twentieth 

 part of the bulk of the blood. 



I know it may be faid, that my method of making thcfe experi- 

 ments was not fufficicntly accurate, to which I can only anlVer, 

 that I conducted them in the belt manner I could devife. 



I made many other oblervations which I did not note down, be- 

 caufe I think I have lufficiently proved, that while the blood is in 

 the veins, or while it remains warm after taken out, there is no 

 other air in it, than that thin and fubtile fluid which pervades not 

 only our bodies, but the lubftance of all folid bodies. 



Now if it be fo, that the blood contains no other air than this 

 fubtile fluid or medium which can pervade all bodies, and that the 

 quantity of common air found in blood after it has llood fome 

 hours, is fo fmall as not to deferve notice, we fhall reject the doc- 

 trine of many medical and chirurgical perlbns, who, \n hen they are 

 not able to aiTign the true cauie of a difeafe, fay, that the blood is in 

 agitation, or in a flate of fermentation, and the like. But I think 

 we may more afluredly than ever, lay it down as a maxim, that 

 every motion in the blood depends on the heart alone, and that we 

 ought rather to fay, the blood is too much condenfed, and cannot 

 eafily be driven through the fmall veflels, wherefore its circulation 

 is not duly performed. 



But when the blood is fo much thickened that it cannot pals 

 through many of the fmall veirels, and thereby its courle is ob- 

 ftru('led, and Hill is driven from the heart with its ufual force, I 

 think that by this means it may be made to burlt through fome of 



Rr 2 



