516 PRACTICE OF PHYSIC. 



take place in different degrees, but that they can take place in 

 different parts of the brain, or at least with respect to the dif- 

 ferent functions, in different degrees. 



As I presume that almost every person has perceived the 

 gradual approach of sleeping and waking, I likewise suppose 

 every person has observed, that, in such intermediate state of 

 unequal excitement, there almost always occurs more or less of 

 delirium, or dreaming, if any body chooses to call it so. There 

 are in this state false perceptions, false associations, false judg- 

 ments, and disproportionate emotions ; in short, all the circum- 

 stances by which I have above defined delirium. 



This clearly shows that delirium may depend, and I shall 

 hereafter endeavour to prove that it commonly does depend, 

 upon some inequality in the excitement of the brain ; and that 

 both these assertions are founded on this, that, in order to the 

 proper exercise of our intellectual functions, the excitement 

 must be complete, and equal in every part of the brain. For 

 though we cannot say that the vestiges of ideas are laid up in 

 different parts of the brain, or that they are in some measure 

 diffused over the whole, it will follow, upon either supposition, 

 that as our reasoning or intellectual operations always require 

 the orderly and exact recollection or memory of associated 

 ideas ; so, if any part of the brain is not excited, or not excita- 

 ble, that recollection cannot properly take place, while at the 

 same time other parts of the brain, more excited and excitable, 

 may give false perceptions, associations, and judgments. 



MDXLVIII. It will serve to illustrate this, that the col- 

 lapse in sleep is more or less complete ; or that the sleep, as 

 we commonly speak, is more or less profound : and therefore, 

 that in many cases, though sleep takes place to a considerable 

 degree, yet certain impressions do still take effect, and excite 

 motions, or, if you will, sensations in the brain ; but which sen- 

 sations, upon account of the collapsed state of so great a part 

 of the brain, are generally of the delirious kind, or dreams, 

 consisting of false perceptions, associations, and judgments, that 

 would have been corrected, if the brain had been entirely ex- 

 cited. 



Every one, I believe, has observed, that the most imperfect 

 sleeps are those chiefly attended with dreaming ; that dreams, 



