IMPROVED. Sj 



the Veins run along the Sides of the Arteries In the 

 Brain, as they do through all the reft of the Body, 

 but they rife from the Extremities of the Arteries 

 in the Cineritious or Afh-colour'd external Subftance, 

 and go draight to difcharge themfelves into the <S/- 

 nus's of the Dura Mater. 



From the Blood, which is brought to the Brain 

 by the C-xrotidal and the Vertebral Arteries, is fe- 

 parated (by the Glands which make the Cineritious cineritions 

 and Cortical Sublbnce) its fineft Parts, called Ani- Subilance, 

 mal Spirits, which are received from the Glands ^'^hat. 

 by the Fibres of the Medullary Subftance, which is 

 the Origin or Spring of all the Nerves in Men, 

 Beafts, <3c. And each Nerve, therefore, is a 

 Bundle of very fmall Tubes or Pipes, of which fome 

 are no bigger than the Hundredth Part of a Hair ; 

 and thefe Tubes are the Excretory Dufts or Dif- 

 charging Veiiels of the Cineritious or Cortical Sub- 

 fiance. And this does not only appear from the 

 Strufture of the Brain^, but by Senfation likewife 

 we are afTured, that there is fuch a Fluid as we call 

 Animal Spirits in the Nerves ; which muft be done 

 either by the Subftance of the Nerve, or the Fluid 

 which is contained in the Nen^e. If by the Sub- 

 ftance of the Nerve, it muft be by a Vibration from 

 tiie Part upon which the ImpreiTion is made to the 

 Brain, 



Now there can be no Vibration from the Im- No Vlbra- 

 preiTion of external Obje^ upon Animal Nerves, tion in the 

 (which are flack, and furroanded all along by other ^^""^'f^f' 

 Bodies) is evident ; and therefore Senfation muft be impreffion 

 made by the Fluid in the Nerves. The Motion of of External 

 this Fluid is not fwiit and rapid, as is generally Objects, 

 fuppofed, but flow and languid ; feeing all its Mo- 

 tion proceeds from the Dilatation of the Arteries 

 which comprefs the foft Subftance cf the Nerves^ 

 and from the Force by which it is thruft through, 

 the Glands of the Brain. And when the Nerves 

 are full of this fme Fluid, the Impreffion of Objedls 

 may be communicated to the Brain without any 



quick 



