on sleep and sleeplessness-第4部分

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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…



。