on sleep and sleeplessness-第4章

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concentration；　or　natural　recoil；　of　the　hot　matter　inwards　＇towards



its　centre＇；　due　to　the　cause　above　mentioned。　Hence　restless　movement



is　a　marked　feature　in　the　case　of　a　person　when　drowsy。　But　where



it　＇the　heat　in　the　upper　and　outer　parts＇　begins　to　fail；　he　grows



cool；　and　owing　to　this　cooling　process　his　eye…lids　droop。



Accordingly　＇in　sleep＇　the　upper　and　outward　parts　are　cool；　but　the



inward　and　lower；　i。e。　the　parts　at　the　feet　and　in　the　interior　of



the　body；　are　hot。



　　Yet　one　might　found　a　difficulty　on　the　facts　that　sleep　is　most



oppressive　in　its　onset　after　meals；　and　that　wine；　and　other　such



things；　though　they　possess　heating　properties；　are　productive　of



sleep；　for　it　is　not　probable　that　sleep　should　be　a　process　of



cooling　while　the　things　that　cause　sleeping　are　themselves　hot。　Is



the　explanation　of　this；　then；　to　be　found　in　the　fact　that；　as　the



stomach　when　empty　is　hot；　while　replenishment　cools　it　by　the



movement　it　occasions；　so　the　passages　and　tracts　in　the　head　are



cooled　as　the　'evaporation'　ascends　thither？　Or；　as　those　who　have　hot



water　poured　on　them　feel　a　sudden　shiver　of　cold；　just　so　in　the　case



before　us；　may　it　be　that；　when　the　hot　substance　ascends；　the　cold



rallying　to　meet　it　cools　＇the　aforesaid　parts＇　deprives　their



native　heat　of　all　its　power；　and　compels　it　to　retire？　Moreover；　when



much　food　is　taken；　which　＇i。e。　the　nutrient　evaporation　from　which＇



the　hot　substance　carries　upwards；　this　latter；　like　a　fire　when　fresh



logs　are　laid　upon　it；　is　itself　cooled；　until　the　food　has　been



digested。



　　For；　as　has　been　observed　elsewhere；　sleep　comes　on　when　the



corporeal　element　＇in　the　'evaporation'＇　conveyed　upwards　by　the



hot；　along　the　veins；　to　the　head。　But　when　that　which　has　been　thus



carried　up　can　no　longer　ascend；　but　is　too　great　in　quantity　＇to　do



so＇；　it　forces　the　hot　back　again　and　flows　downwards。　Hence　it　is



that　men　sink　down　＇as　they　do　in　sleep＇　when　the　heat　which　tends



to　keep　them　erect　（man　alone；　among　animals；　being　naturally　erect）



is　withdrawn；　and　this；　when　it　befalls　them；　causes



unconsciousness；　and　afterwards　phantasy。



　　Or　are　the　solutions　thus　proposed　barely　conceivable　accounts　of



the　refrigeration　which　takes　place；　while；　as　a　matter　of　fact；　the



region　of　the　brain　is；　as　stated　elsewhere；　the　main　determinant　of



the　matter？　For　the　brain；　or　in　creatures　without　a　brain　that



which　corresponds　to　it；　is　of　all　parts　of　the　body　the　coolest。



Therefore；　as　moisture　turned　into　vapour　by　the　sun's　heat　is；　when



it　has　ascended　to　the　upper　regions；　cooled　by　the　coldness　of　the



latter；　and　becoming　condensed；　is　carried　downwards；　and　turned



into　water　once　more；　just　so　the　excrementitious　evaporation；　when



carried　up　by　the　heat　to　the　region　of　the　brain；　is　condensed　into　a



'phlegm'　（which　explains　why　catarrhs　are　seen　to　proceed　from　the



head）；　while　that　evaporation　which　is　nutrient　and　not　unwholesome；



becoming　condensed；　descends　and　cools　the　hot。　The　tenuity　or



narrowness　of　the　veins　about　the　brain　itself　contributes　to　its



being　kept　cool；　and　to　its　not　readily　admitting　the　evaporation。



This；　then；　is　a　sufficient　explanation　of　the　cooling　which　takes



place；　despite　the　fact　that　the　evaporation　is　exceedingly　hot。



　　A　person　awakes　from　sleep　when　digestion　is　completed：　when　the



heat；　which　had　been　previously　forced　together　in　large　quantity



within　a　small　compass　from　out　the　surrounding　part；　has　once　more



prevailed；　and　when　a　separation　has　been　effected　between　the　more



corporeal　and　the　purer　blood。　The　finest　and　purest　blood　is　that



contained　in　the　head；　while　the　thickest　and　most　turbid　is　that　in



the　lower　parts。　The　source　of　all　the　blood　is；　as　has　been　stated



both　here　and　elsewhere；　the　heart。　Now　of　the　chambers　in　the　heart



the　central　communicates　with　each　of　the　two　others。　Each　of　the



latter　again　acts　as　receiver　from　each；　respectively；　of　the　two



vessels；　called　the　'great'　and　the　'aorta'。　It　is　in　the　central



chamber　that　the　＇above…mentioned＇　separation　takes　place。　To　go



into　these　matters　in　detail　would；　however；　be　more　properly　the



business　of　a　different　treatise　from　the　present。　Owing　to　the　fact



that　the　blood　formed　after　the　assimilation　of　food　is　especially



in　need　of　separation；　sleep　＇then　especially＇　occurs　＇and　lasts＇



until　the　purest　part　of　this　blood　has　been　separated　off　into　the



upper　parts　of　the　body；　and　the　most　turbid　into　the　lower　parts。



When　this　has　taken　place　animals　awake　from　sleep；　being　released



from　the　heaviness　consequent　on　taking　food。　We　have　now　stated　the



cause　of　sleeping；　viz。　that　it　consists　in　the　recoil　by　the



corporeal　element；　upborne　by　the　connatural　heat；　in　a　mass　upon



the　primary　sense…organ；　we　have　also　stated　what　sleep　is；　having



shown　that　it　is　a　seizure　of　the　primary　sense…organ；　rendering　it



unable　to　actualize　its　powers；　arising　of　necessity　（for　it　is



impossible　for　an　animal　to　exist　if　the　conditions　which　render　it　an



animal　be　not　fulfilled）；　i。e。　for　the　sake　of　its　conservation；　since



remission　of　movement　tends　to　the　conservation　of　animals。











　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　　…THE　END…



。