C 90 ) 



I afterwards examined his gills, or tliofe parts hanging under 

 the throat, and there I favv it running in an inconceivable num- 

 ber of veilels ; man}' of v;hich were fo minute, that numbers of 

 them taken together \Vould not equal the fize of a hngle hair : 

 but it was impoihble for me to trace the circulation in them, by rea* 

 fon of tlieir imraenfe number, crolfing each other in all diredlions : 

 for the rednefs which we obferve in a cock's comb and gills, proceeds 

 entirely fiom tlie great number of blood-velTels on their furface, 

 where they are only covered with a thin tranfparent fkin. 



After this, I made my obfervations on white Rabbits, by placing 

 their ears before the microfcope ; but, with -all my pains, I could 

 not do more than fee the Blood running with great fwiftnefs througli 

 the ■arteries and veins. When I plucked oft" tlie ihort hairs from tlie 

 extremities of the ears, becaufe they obftrufted my fight, lobferved, 

 that the pulling off" each hair had broken or injured feveral of the 

 veflels, and caufed an effufion of blood. From hence I gatliercd the 

 rcafon, why I had perceived that the pulling out any hairs from the 

 back of my hand produced a rednefs in the part ; and I now con- 

 cluded, that we cannot pull out a fingle hair from any part of our 

 bodies, w hile fuch hair is growing, without injuring i'omc vefl'els, fo 

 as to caufc the Blood to flart. 



But my greateft expectation of fuccefs, was placed on a Bat, be- 

 caufe I conceived that the membrane, or fkin, which ferves this ani- 

 mal for wings, muft be fo thin and tranfparent, as to afford a view 

 of the veffels. And, having procured one of thefe creatures, I put it 

 into a glafs and examined it by the microfcope. Here I fav/ the mo- 

 tion of the Blood, both in the arteries and viens, moft diftinflly, and 

 fully to my fatisfa(5tion, though by no means fo clearly as is to be feen 

 in f'ihes ; firft, becaufe the membrane compofingthe bat's wing, is 

 not fo tranfparent ; fecondl y, becaufe there is more of the watery part 

 (or ferum, as it is called) in the Blood of fiflies than in terreftrial 



