86 Mifrofcopical Appear am es of Blood. [Book IX. 



c The red particles of the blood, improperly calle4 

 globules, are flat in all animals, and of very different 

 fizes in different animals. In man they are fmall, as 

 fiat as a milling, and appear to have a dark fpot in the 

 middle. In order to fee them diftinctly, I dilute the 

 blood with frefti ferum. My predeceffors, not having 

 thought of this, could not fee them diftinctly. And 

 Lewenhoeck in particular, imagining a round figure 

 finteft for motion, concluded they muft be round in the 

 human body ; though he and others allowed that in 

 frogs, &c. where they viewed them diftinctly, from 

 the blood being thinner, they were flat. Now I prove 

 that they are flat in all animals. In the human blood, 

 where thefe particles are fmall, it is difficult to deter- 

 mine what that black fppn is, which appears in the 

 center of each. Some hate concluded that it was a 

 perforation ; but in a frog, where it is fix times as 

 large as in a man, it is eafy to (hew that it is not a 

 perforation, but on the contrary, is a little folid, which 

 is contained in the middle of a veficle. Inftead, there- 

 fore, of calling this part of the blood r&& globules, I 

 fhould call it red veficles ; for each particle is a flat ve- 

 ficle, with a little folid fphere in the center. 



f I find that the blood of all animals contains veficles 

 of this fort. In human blood there are millions of 

 them, and they give it the red colour j but in infects 

 they are white, and lefs numerous in proportion than 

 in man and quadrupeds. As they are flat in ail ani- 

 mals, I fufpect that ftiape is a circumftance of im- 

 portance, but can be altered by a mixture with differ- 

 ent fluids. And I find, that it is by a determinate 

 quantity of neutral fait contained in the ferum, that this 

 fluid is adapted to preferving thefe veficles in their flat 

 fhape: for if they are mixed with water, they become 

 found, and diffolve perfectly , but add a little of any 



neutral 



