( 300 ) 



In order to exhibit more clearly to view, the formation of this 

 afcending veflel, which I call a blood-vellcl, and from whence the 

 lides of the large cavities in the Rufh proceed, I took one of 

 the fmallell of tbofe veffels, the fides of which I tore alunder as 

 exaftly as I could, and placed them before the microfcope, that I 

 might caule as accurate a drawing as pofTible to be made of them. 



Fig. 35, RV, reprefents one of thefe fmall veflels, confilling of 

 many ftill Imallcr ones, out of which fmall veffels arife a great num- 

 ber of horizontal veflels, and of thefe lall veflels, as I have faid, the 

 tubes of Rnflies are compofed, and thefe veflels as broken off from 

 thofe tubes of the Rufli are piftured at S T and W. 



This blood-velTcl (as I call it), R V, from which fuch a wonder- 

 ful produdion and fo many veflels arife is fo thin, that meafured 

 by the naked eye, I mufl: fay, that it is not a twenty-fifth part 

 the thicknefs of a hair. 



But what feemed to me ftill more wonderful was, that I thought 

 I faw from the afcending blood- veflels reprefented in fig. 34, at Q N, 

 or fig. 35, at RV, and from the horizontal veflels which arofe 

 from thofe blood- veflels, a matter or fubflance protruded, which im- 

 mediately extended itfelf in length, and appeared to form a mem- 

 brane. But when I examined this nearer, I faw that the fide of 

 the Rufli's tube, Q, L INI N, was not a Ample membrane, but that 

 each feparate part forming that fide was manifeftly hollow, and 

 that the cavity was furrounded on all fides with a wonderfully thin 

 membrane. This cavity is fliewn mfg. 35, about and before S. 



Upon difcovering this, T placed the fides fo broken off from the 

 tube of the Rufli, before a deeper magnifier, and diredled the en- 

 graver to make a drawing of two of the parts, in which he could 

 moft plainly diftinguifh the cavities ; and thefe are fhewn in Jig. 34, 

 between X and Y. 



Now if we fuppofe that all thefe cavities, and each of thofe 

 whereof the fide of one of the tubes in a Rufh confifts, cannot be 

 formed but of an incredible number of fmall veflTels, in like manner 



