2 5 4 OF SLEEP. SECT. XVIII. 2 > 



motion, which are more immediately neceflary to life, as thofe 

 caufed by internal ftimuli, for inftance the pulfations of the 

 heart and arteries, or thole catenated with pleafurable fenfa- 

 tion, as the powers of digeftion, continue to ftrengthen their 

 habits without interruption. Thus though man in his fleeping 

 ftate is a much lefs perfect animal, than in his waking hours ; 

 and though he confumes more than one third of his life in this 

 his irrational fituation ; yet is the wifdom of the Author of na- 

 ture manifeft even in this feeming imperfection of his work. 



The truth of this aflertion with refpect to the large mufcles 

 of the body, which are concerned in locomotion, is evident ; 

 as no one in perfecl: fanity walks about in his fleep, or performs 

 any domeftic offices ; and in refpect to the mind, we never ex- 

 ercife our reafon or recollection in dreams; we may fometimes 

 feem diffracted between contending paflions, but we never 

 compare their objects, or deliberate about the acquifition of thofe 

 objects, if our fleep is perfect. And though many fynchronous 

 tribes or fucceflive trains of ideas may reprefent the houfes or 

 walks, which have real exiftence, yet are they here introduced 

 by their connexion with our fenfations, and are in truth, ideas 

 of imagination, not of recollection. 



2. For our fenfations of pleafure and pain are experienced 

 with great vivacity in our dreams ; and hence all that motley 

 group of ideas, which are caufed by them, called the ideas of 

 imagination, with their various aflbciated trains, are in a very 

 vivid manner acted over in the fenforium ; and thefe fometimes 

 call into action the larger mufcles, which have been much aflb- 

 ciated with them ; as appears from the muttering fentences, 

 which fome people utter in their dreams, and from the obfcure 

 barking of fleeping dogs,and the motions of their feet and noftrils. 



This perpetual flow of the trains of ideas, which conftitute our 

 dreams, and which are caufed by painful or pleafurable fenfa- 

 tions, might at firft view, be conceived to be an ufelefs expen- 

 diture of fenforial power. But it has been fhewn, that thofe 

 motions, which are perpetually excited, as thofe of the arterial 

 fyftem by the ftimulus of the blood, are attended by a great ac- 

 cumulation of fenforial power, after they have been for a time- 

 fufpended , as the hot- fit of fever is the confluence of the 

 cold one. Now as thefe trains of ideas caufed by fenfation are 

 perpetually excited during our waking hours, if they were to be 

 fufpended in fleep like the voluntary motions, (which are exerted 

 only by intervals during our waking hours,) an accumulation 

 of fenforial power would follow , and on our waking a delirium 

 would fupervene, fince theie ideas caufed by fenfation would 

 be produced with fuch energy, that we (houid miftake the trains 



of 



