^f "tllE PHlLOSOPHir 



the vibrations of thefe cords, the various imprcffions and 

 modifications of feeUng are conveyed to the brain. Others, 

 with more plaufibiHty, have fuppofed, that the nerves are 

 affemblages of fmall tubes ; that a fubtile fluid, fometimes 

 called afiimal /pints, is fecreted in the brain and fplnal mar- 

 row ; and that by the influence or motions of this fluid all 

 the fenfations of animals are tranfmitted to the fenforium, 

 or general repolitory of ideas. But it is needlefs to dwell 

 upon a fubject covered with darknefs, and which all the 

 efforts of human powers will probably never bring to light. 



Anatomifts have defcribed forty pair of nerves. Ten of 

 them proceed from the medulla oblongata of the brain, and 

 thirty from the fpinal marrow. Thefe nerves, by fending 

 off innumerable ramifications, are dlflrlbuted, like a net- 

 work, over every part of the body, till they terminate, in the 

 form of a minute papillae, upon the fl:in. That the nerves 

 are the i^nmediate inftruments of fenfation, as well as of muf- 

 cular motion, has been proved by a thoufand uncontro- 

 vertible experiments. When the trunk of the fciatic nerve 

 is cut, the thigh and leg on that fide inflantly lofe all motion, 

 and all fenfe of pain, below the incifion, and neither time 

 nor art can ever reflore the power of feeling or of moving. 

 But the parts betv/een the incifion and the fpinal marrow, 

 v^hich is a continuation of the brain, retain their ufiial de- 

 grees both of motion and of fanfation. From this experi- 

 ment, it is evident, that the nerves are the organs by which 

 fenfation and motion are efFedted, and that, for thefe im- 

 portant purpofes, an uninterrupted connexion between any 

 particular nerve and the brain, or fpinal marrow, is indif- 

 penfible. 



This fKetch of the human fabric requires an apology to 

 anatomical readers, who mull: be fenfible of its many imper- 

 fe6lions. To perfons who have not ftudied that curious and 

 #feful fcience, I imagined a general view of the jftrudlure of 



