OF SLEEP. SECT. XVIII. i. 



caufes of Jleep. dtmofphere with lefs oxygene. 

 Comprejfton of the brain in fpina bifida. By whir- 

 ling on an horizontal wheel. By cold. 21. Defini- 

 tion of jleep. 



I. THERE are four fituations of our fyftem, which 

 in their moderate degrees are not ufually termed dif- 

 eafes, and yet abound with many very curious and 

 inftrudtive phenomena ; thefe are fleep, reverie, 

 vertigo, drunkennefs. Thefe we fhall previoufly 

 confider, before we ftep forwards to develop the 

 caufes and cures of difeafes with the modes of the 

 operation of medicines. 



As all thofe trains and tribes of animal motion, 

 which are fubje&ed to volition, were the lafl that 

 were caufed, their connection is weaker than that 

 of the other claffes ; and there is a peculiar circum- 

 ftance attending this caufation, which is^ that it is 

 entirely fufpended during ileep ; whilft the other 

 claffes of motion, which are more immediately ne- 

 ceflary to life, as thofe caufed by internal fUmuli, 

 for inftance the pulfations of the heart and arteries, 

 or thofe catenated with pleafurable fenfation, as the 

 powers of digeftion, continue to ftrengthen their 

 habits without interruption. Thus though man in 

 his fkeping (late is a much lefs perfeft animal than 

 in his waking hours ; and though he confumes more 

 than one third of his life in this his irrational fitua- 

 tion ; yet is the wifdom of the Author of nature 

 manifeit. even in this feemin-g imperfection of his 

 work ! 



The truth of this affertion with refpecl; to the large 

 mufcles of the body, which are concerned in loco- 

 motion, is evident ; as no one in perfect fanity 

 walks about in his fleep, or performs any domeftic 

 offices ; and in refpeft to the mind, we n^ver ex- 

 ercife our reafon or recollection in dreams \ we may 

 fometimes feem diftrafted between contending paf* 



