( 101 ) 



Proceeding farther in my inquiries, I took the head of a Sheep, 

 and upon examining its Brain, I alfo found in the corticle, 

 a great number of wonderfully minute blood-veflels, in which 

 I could difcover the fubftance which gives the blood its red 

 colour ; thefe veflels alfo gave the corticle a darkifli complex- 

 ion. I often contemplated this incomprehenfible multitude of 

 exquiiitely minute blood-veflels, merely for the pleafure I took 

 in viewing them. For I fusv almoft all of them again divide 

 into branches ; and I moreover took notice of a great number 

 of globules, each about a fixth part tlie fize of a globule of 

 human blood, and which, I judged, iifued from the vell'cls which 

 were broken ; and 1 coiicluded, that lix of thofe globules would 

 join to make up one globule of blood when they palled into 

 larger veflels, for they were very inferior in tranfparency to the 

 other globules adjoining. I alfo unagined that thele globules, 

 of which fix would m.ake up an ordinary fized globule, when they 

 came to veflt-Is fo fmall as not to admit them, muft be again 

 divided into ftill fmaller pai-ts, and then thofe vellels would become 

 colourlefs. And, in order more clearly to giA-c the reader feme 

 idea of the incomprehenf ble flendernefs of the blood veflels wliich 

 are formed in the brain, I have made a computation of their flze, 

 judging by the eye, and by comparifon wnth a large grain of fand ; 

 I take it then for a certain pofition that thofe globules which tinge 

 our blood with a red colour are, when perfecT:, of fuch a fize, that 

 one hundred of them laid fide by fide, do not more than 

 IQO equal the thicknefs or axis of a grain of fand, and 

 '00 confequently, that a million of globules of blood are 

 1,000,000 equal to a large grain of fand. I next obfervc the blood- 

 •5* veflels in the Brain, refpeAing which I am certain, that 



64,000,000 if one globule of blood was divided into fixty-four parts, 

 """ none of fuch parts could pafs through one of thofe vef- 



fels ; for I Hate the diameter of one of thofe vell'els to be as i; and- 



