SLEEP. 



It will eafily be underftood that circumilances oppofite to 

 thofe juft enumerated are favourable to fleep. Bodily ex- 

 ercife with tranquillity of mind, and abfencejof all excitation, 

 are the moft important of thcfe. A full repaft is often fol- 

 lowed by fleep, even in animals, as'dogs. The dillention 

 of the ilomach excites the circulation, and thus brings on a 

 condition of the brain favourable to fleep. Various vege- 

 table fubftances taken into the ilomach aft on the brain in 

 the fame way. Intenfe cold, affefting the whole body, ex- 

 haufts the animal powers and brings on fleep, which is 

 fpeedily 'fatal. See Cold. 



Sleepinefs, when it occurs naturally, after our daily oc- 

 cupations, is marked, firft, by a fenfe of mufcular fatigue, 

 particularly in the long mufcles : it may be experienced in 

 various parts, according as they have been more exercifed. 

 We begin to gape ; the intellcftual funftions languifli ; cu- 

 riofity is blunted ; attention becomes painful ; and a great de- 

 fire of repofe is fell over the whole body. The imprefTions 

 on the external I'enfes are indiitinct ; we cannot read well, 

 nor does the memory ac"f with its ufual force or order : an 

 uneafy fenfation is perceived in the eye ; the upper eye -lid 

 falls in fpite of every effort to keep it elevated. Now the 

 mufcles of the whole body are more or lefs relaxed : hence 

 the head inclines forwards, and the whole body would come 

 to the ground if the perfon were itaading. The lenfe of 

 hearing feems to be fufpended lalt ; we hear and underltand 

 the converfation of thofe near us, when the eyes no longer 

 att. Now the fucceffion of our mental operations becomes 

 quite involuntary ; and a kind of delirium takes place, in 

 which the trains of thought preferved in the memory fuc- 

 ceed according to their natural affociations and connec- 

 tions. Thefe operations are then fufpended, and fleep is 

 complete. 



Refpefting the (late of the body in fleep we have very 

 little to add to our general account already given. In com- 

 plete fleep the body is perfeftly motionlefs ; the fenfes are 

 not affedled by their refpeftive external objedts, unlefs the 

 impreflions (hould be ftrong enough to aroufe us. Hunger 

 and third are not felt ; nor are we confcious of the neceflity 

 of emptying the bladder or bowels, until the diftention is 

 fufficient to waken us. The functions of the organic life 

 go on uninterruptedly ; digeftion, chylitication, and the 

 converfion into faeces, abforption, circulation, refpiration, 

 nutrition, fecretion, are all continued. There mav be feme 

 flight modifications, but they are unimportant. 



After the fleep has laded long enough to reltore the ani- 

 mal powers, we awake, without any change or occurrence 

 which can be fliewn to affeft particularly the brain or other 

 parts, of which the atlion was fufpended by fleep. We 

 open our eyes, and often rub them. We move the limbs 

 and ilretch them ; and in a few feconds we have the full ufe 

 of our fenfes, intelleftual faculties, voice and voluntary 

 mufcles, and they recover their powers of aftion com- 

 pletely. 



There are rare examples of individuals, who have gone 

 on deeping for days, weeks, and mouths : but thefe hifto- 

 ries are not accompanied with fuch particulars as would ena- 

 ble us to judge of the caufe for fuch a deviation from the 

 ordinary courfe of nature. 



Sleep, Somnus, in Mythology, the fon of Erebus and of 

 Night, according to Homer and Hefiod, and the brother of 

 Mors or Death. 



Virgil (jEn. vi. v. 278.) affigns to this deity an abode 

 with death, in the fubterraneous or invifible world. 



Statius and Ovid place the chief refidence, or great palace 

 of Somnus on our earth, in the country of the Cimmerians ; 

 no country agreeing better with fleep than that which is 



overfpread with eternal darknefs. Tlieb. x. v. 8410 117. 

 Met. xi. v. 592 to 645. 



Dreams werejthe children of fleep ; Ovid names three of 

 them, t'iz. Morpheus, Phobetor, and Phantafia. 



This deity is moft commonly reprefented by the artifts as a 

 foft youth, ftretched at his eafe on a couch, refting his head 

 on a lion's (kin, and fometimes on a lion ; with one arm 

 either a little over or under his head, and the other dropping 

 negligently by the fide of the couch, and cither holding 

 poppies, or a horn with the juice of poppies in it. He is 

 often winged, and much refembles a little Cupid, from 

 whom he is diilinguifhed by the lizard (^an animal fuppofed 

 to fleep half the year) placed at his feet. There is fcarcely 

 any one of the deities that is more fully and particularly de- 

 fcribed by tlie poets than this deity of fleep. Spence'g Po. 

 lymctis, p. 263, &c. 



Sleep of Plants, Somnus Plantarum, in Vegetable Phyfto- 

 logy, is a term ufed by Linnaeus, to exprefs a peculiar itate 

 in the conftitution of many plants during the night, evinced 

 by a change of pofition, generally a drooping, or a folding 

 together, of their leaves or leaflets. Such a change, being 

 occafioned by the withdrawing of the (limulus of light, i« 

 probably a ftate of reil to their vital funtlions, and there- 

 fore the above terra is not fo hyperbolical as at fir(t appears. 

 Linnxus has given a curious treatife on this fubjeft, in the 

 Amanitates j^cademkie, v. 4. 333. The phenomenon itfelf 

 had been noticed long before, by Acofta and Profper Al- 

 pinus, in the Tamarind-tree ; and the latter points out feve- 

 lal parallel inftances in other leguminous plants with pin- 

 nated leaves, natives of Egypt. It is indeed moft remark- 

 able in fuch plants. Herbs with ternate leaves, as the Tre- 

 fofl and Oxalis, deep with their leaflets folded together ia an 

 ereft poiture ; and Phny has obferved that the former of 

 thefe alTumes that pofition at the approach of ftorms. 

 Cloudy weather, no doubt, produces this efteft, in propor- 

 tion as the plant is in vigour, and the (limulus of preceding 

 fun-fhine has been ftrong. Not that a celTation or diminution 

 of heat appears to caufe the change alluded to ; for Lin- 

 nxiis has well remarked, from observing ftove-plants, that 

 fuch is not the cafe. It is the withdrawing of a confiderable 

 portion of light. The more young and tender the plant, 

 the more fenfibly is it affedled by this caufe. 



Linnaeus has, in the above-mentioned treatife, elaborately 

 defcribed the various pofitions which the leaves of different 

 plants allume in their fleep. In general, it may be remarked 

 that they cover, or fold together, the upper furfaces of 

 their leaves, expofing the under, which latter is almoit uni- 

 formly impatient of light. This is fo much the cafe, that 

 we cannot but fufpeft the eifeft of the returning hght upon 

 the backs of fuch leaves, may be the immediate caufe of their 

 withdrawing from it, and thus the upper furface becomes 

 necefTarily prefented to its rays. 



A fimilar effedl of light is feen in many flowers, particu- 

 larly of the compound tribe. But the expanfion of thefe 

 is regulated by other and more abllrufe laws, which often 

 limit their changes to certain hours of the day, partly, 

 though not abfolutely, in^pendently of light. Many of 

 the Campion tribe, efpecially, unroll their delicate petals in 

 an evening only, in a precife and determinate manner, not to 

 be attributed either to the prefence or the abfence of light. 

 So the moving-plant, Hedyfarum gyrans, performs its cu- 

 rious gyrations with apparently perfedl indifference as to the 

 degree of light to which it is expofed, provided the fur- 

 rounding atmofphere be warm and (till. The clofing or 

 drooping of flowers, moreover, when it depends only on the 

 diminution of light, generally anfwers an evident fecondai-y 

 purpofe, in (heltering the organs of impregnation from the 



injurious 



