38 The Anatomy of aWOKSV.. Chap. IV. 



or Arch which riles between the Brain and the Medulla Ob- 

 longata y and I'erves to bear up the upper Part of the Brain, 

 that it may not prefs too hard upon the fubjacent Parts. 

 Thf Uf ofth Now as to its Adion and Ufe, it is very 



Brain- ^ Certain, the Brain, according to the Philo- 

 fophcrs Terms, is the chief Seat of the Ani- 

 mal Faculty, as the Heart is the Fountain of the Vital. 

 The Animal Spirits being prepared out of its Parenchyma^ 

 or marrowy Subftnnce, and from thence conveyed into the 

 Nerves, which communicate Senfe and Motion to all Parts 

 of the Body. 



Thefe Spirits are firfl: of all form'd out of 



slf" ^^'^ ^^'^'^'' °^ ^" °^^^^'' ^^*^''<^s, out of the Ar- 



^"' ■"* terial Bloody which is conftantly fent by the 



Heart to the Brain, where there aie innumerable Twigs dif- 

 perfed, not only throuo;h its cortical or greyifh Stibftance, 

 but alfo through its white and meJulhry Subllance ; fome 

 of which Twigs fpring from the Plexus Choroides and 

 Mete Mirali's above defcribed, and others from tlie Ca- 

 rotidi themfclves immediately. The fuperfiuous Serum 

 is feparated by the Glands ; and that Portion of the Blood 

 "which is not changed to animal Spirits, is taken up by the 

 A''eins, and returned bacic again from whence it came. As 

 foon as thefe Spirits are elaborated, or rather, as foon as 

 the Blood has undergone fo many different Mortifications 

 •and Changes in the capillary or hair-like Veflels of the 

 Brain, as to render its Particles fine enough to pafs through 

 the inner medullar Subftance, they then enter thofe Fibres 

 which compofe it, and feem. to be no other than a large 

 Bundle of Tuhuli or h'.tle Pipes, which (if the Comparifon 

 may beufed) fomewhat obferve the fame Oeconomy with 

 hofe of the Kidnies, which pafs fi'om the external glandu- 

 lar Parts to Lhe Caruncula Papiilare. Thefe little Particle?, 

 or rather Spirits, are conveyed by the aforefaid Tuhuli to the 

 tipped Procefles of the Medulla Oblongata., to wit, the Cor- 

 Pora Striata^ Nates^ and Telle:^ ^c. and are there emptied 

 into the Nerves, whofe inner Subftance is white and fibrous, 

 like the Medulla from whence they fpring. 

 *^h ' Uf' After this ihort Account of the Formation 



of the animal Spirits, the next Thing that, 

 occurs, is in what Manner they become the Inftruments of 

 Senfe and Motion. In order to give the Reader a general 

 Idea of this, which is as much as can be done in fo fmall a 

 Treaiife^i: will be necdiary in the firfl PUce,to confider the 



Subftance 



