OP SLEEP. 199 



and nearly all the excretions (except that of the semen, 

 which is indeed rather unusual) suppressed. (A) 



321. The remote causes of sleep are evident.* To 

 say nothing of narcotics, it is induced by the expen- 

 diture of the animal powers from previous fatigue or 

 watchfulness, also by habit, darkness, silence, rest, &c. 

 which acquire their somniferous powers in some mea- 

 sure from habit, by mild, continued, and uniform im- 

 pressions upon certain senses, v. c. the murmur of a 

 rivulet or the view of a field of standing corn agitated 

 by the wind, a previous meal, intense cold applied to 

 the surface, and other modes of deriving blood from the 

 head, as pediluvia, clysters, profuse hemorrhages. 



322. These remote causes may induce the proximate 

 cause, which, upon mature consideration, we think pro- 

 bably consists in a diminished or impeded flow of oxyge- 

 nated (arterial) blood to the brain, for that fluid is of the 

 highest importance, during the waking state, to the 

 reaction of the sensorium upon the senses and voluntary 

 motions.t 



* Although the lethargic winter torpor of the Alpine marmot, the cricetum, 

 and many other mammalia brutes, differs importantly from the sleep now spoken 

 of, modern observations respecting this torpor have shewn, that, in their pheno- 

 mena and remote causes, both correspond and mutually elucidate each other. 

 Consult, for instance, Sulzer, Naturgeschichte ties Hamsters, p. 162. 



Spallanzani, Sur la Respiration. Geneva. 1803. 8vo. 



Mangili, and C. UJ. Von Salis in the latter's and Steinmullcr's Alpiua. 

 T.iv. 1809. 



Cuvier, Analyse des Travaus de la Classc Physique de I' Institute 1807. 



f Those who wish to know and compare other opinions upon the causes of 

 sleep, may consult 



M. de Grimaud, Me'moire sur la Nutrition. Petersb. 1789. 4to. p. 194. 



Am. Wienholt, Heilkraft des thierischen Magnetismus. T. ii. p. 439. 



H. Nudow, Vcrsuck einer Theorie des Scklafs.. K<ENINGSBERG. 1791. gvo. 



Step*. 



