VESANIJE. 513 



ing upon a certain state of our corporeal part. See Halleri 

 Prim. Lin. Physiolog. 570. See Boerhaavii Inst. Med. 

 581. 696*." (Physiology, XXXI.)" 



MDXXXVIII. Admitting this proposition, I must in 

 the next place assume another, which I likewise suppose to be 

 demonstrated elsewhere. " (Physiology, CXVII.)." This is, 

 that the part of our body more immediately connected with the 

 mind, and therefore more especially concerned in every affection 

 of the intellectual functions, is the common origin of the nerves ; 

 which I shall, in what follows, speak of under the appellation 

 of the brain. 



MDXXXIX. Here, however, in assuming this last pro- 

 - position, a very great difficulty immediately presents itself. 

 Although we cannot doubt that the operations of our intellect 

 always depend upon certain motions taking place in the brain, 

 (See Gaub. Path. Med. 523.) ; yet these motions have 

 never been the objects of our senses, nor have we been able to 

 perceive, that any particular part of the brain has more concern 

 in the operations of our intellect than any other. Neither have 

 we attained any knowledge of what share the several parts of 

 the brain have in that operation ; and therefore, in this situa- 

 tion of our science, it must be a very difficult matter to discover 

 those states of the brain that may give occasion to the various 

 state of our intellectual functions. 



MDXL. It may be observed, that the different state of the 

 motion of the blood in the vessels of the brain has some share 

 in affecting the operations of the intellect ; and physicians, in 

 seeking for the causes of the different states of our intellectual 

 functions, have hardly looked further than into the state of the 

 motion of the blood, or into the condition of the blood itself: 

 but it is evident, that the operations of the intellectual functions 

 ordinarily go on, and are often considerably varied, without our 

 being able to perceive any difference either in the motions or in. 

 the condition of the blood. 



MDXLI. Upon the other hand, it is very probable, that the 

 state of the intellectual functions depends chiefly upon the state 

 and condition of what is termed the Nervous Power, or, as we 

 suppose, of a subtile very moveable fluid, included or inherent, 



VOL. II. 2lf 



