On the Circulatioti of the Blood ; that it is not difcoverahle by the fight, 

 in an human body, nor in the bodies of terrejlrial animals : the fame 

 completely feen inffl^es, and the nature of it particularly defcribed. 



JL HE Blood is compofed of exceeding fmall particles, named, 

 globules, # which, in moft animals, are of a red -f- colour, I'wimming 

 in a liquor, called, by phyficians, the ferum ; and by means of thefe 

 globules the motion of the Blood becomes vifible, which otherwife 

 would not be difcoverahle by the fight. Thefe particles, or globules, 

 are fo minute, that one hundred of them, placed fide by fide, would 

 not equal the diameter of a common grain of fand ; confequently, a 

 grain of fand is above a million times the fize of one fuch globule. 



I have often endeavoured to view the circulation of the blood in 

 terreftrial animals, but without fuccefs, by reafon that no parts of 

 their bodies were fuflficiently tranfparent. Among others, I tried 

 the experiment with a young Cock ; which I wrapped in a cloth, in 

 order to keep him quiet, leaving out only his head ; and infpe6led 

 his comb, but could not therein perceive the motion of the Blood : 



* Later writers contend, that the particles of Blood are not fpherical, as this word imports, 

 but plane, or of a flat (hape ; and tliis Mr. Leeuwenhoek admits to be true with regard to 

 fifhes. However, the word globules is always ufed to denote the component particles of the 

 circulating fluid. 



f la fome fifhes the Blood is not of a red colour, and alfo in many infe<fls, which have been 

 therefore improperly denominated exfangues, or bloodlefs. 



M 



