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on sleep and sleeplessness-第3节

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undergoing a change; is converted into blood; and makes its way to



their source 'the heart'。 We have treated of all this when



discussing the subject of nutrition; but must here recapitulate what



was there said; in order that we may obtain a scientific view of the



beginnings of the process; and come to know what exactly happens to



the primary organ of sense…perception to account for the occurrence of



waking and sleep。 For sleep; as has been shown; is not any given



impotence of the perceptive faculty; for unconsciousness; a certain



form of asphyxia; and swooning; all produce such impotence。 Moreover



it is an established fact that some persons in a profound trance



have still had the imaginative faculty in play。 This last point;



indeed; gives rise to a difficulty; for if it is conceivable that



one who had swooned should in this state fall asleep; the phantasm



also which then presented itself to his mind might be regarded as a



dream。 Persons; too; who have fallen into a deep trance; and have come



to be regarded as dead; say many things while in this condition。 The



same view; however; is to be taken of all these cases; 'i。e。 that they



are not cases of sleeping or dreaming'。



  As we observed above; sleep is not co…extensive with any and every



impotence of the perceptive faculty; but this affection is one which



arises from the evaporation attendant upon the process of nutrition。



The matter evaporated must be driven onwards to a certain point;



then turn back; and change its current to and fro; like a tide…race in



a narrow strait。 Now; in every animal the hot naturally tends to



move 'and carry other things' upwards; but when it has reached the



parts above 'becoming cool'; it turns back again; and moves



downwards in a mass。 This explains why fits of drowsiness are



especially apt to come on after meals; for the matter; both the liquid



and the corporeal; which is borne upwards in a mass; is then of



considerable quantity。 When; therefore; this comes to a stand it



weighs a person down and causes him to nod; but when it has actually



sunk downwards; and by its return has repulsed the hot; sleep comes



on; and the animal so affected is presently asleep。 A confirmation



of this appears from considering the things which induce sleep; they



all; whether potable or edible; for instance poppy; mandragora;



wine; darnel; produce a heaviness in the head; and persons borne



down 'by sleepiness' and nodding 'drowsily' all seem affected in



this way; i。e。 they are unable to lift up the head or the eye…lids。



And it is after meals especially that sleep comes on like this; for



the evaporation from the foods eaten is then copious。 It also



follows certain forms of fatigue; for fatigue operates as a solvent;



and the dissolved matter acts; if not cold; like food prior to



digestion。 Moreover; some kinds of illness have this same effect;



those arising from moist and hot secretions; as happens with



fever…patients and in cases of lethargy。 Extreme youth also has this



effect; infants; for example; sleep a great deal; because of the



food being all borne upwards…a mark whereof appears in the



disproportionately large size of the upper parts compared with the



lower during infancy; which is due to the fact that growth



predominates in the direction of the former。 Hence also they are



subject to epileptic seizures; for sleep is like epilepsy; and; in a



sense; actually is a seizure of this sort。 Accordingly; the



beginning of this malady takes place with many during sleep; and their



subsequent habitual seizures occur in sleep; not in waking hours。



For when the spirit 'evaporation' moves upwards in a volume; on its



return downwards it distends the veins; and forcibly compresses the



passage through which respiration is effected。 This explains why wines



are not good for infants or for wet nurses (for it makes no



difference; doubtless; whether the infants themselves; or their



nurses; drink them); but such persons should drink them 'if at all'



diluted with water and in small quantity。 For wine is spirituous;



and of all wines the dark more so than any other。 The upper parts;



in infants; are so filled with nutriment that within five months



'after birth' they do not even turn the neck 'sc。 to raise the



head'; for in them; as in persons deeply intoxicated; there is ever



a large quantity of moisture ascending。 It is reasonable; too; to



think that this affection is the cause of the embryo's remaining at



rest in the womb at first。 Also; as a general rule; persons whose



veins are inconspicuous; as well as those who are dwarf…like; or



have abnormally large heads; are addicted to sleep。 For in the



former the veins are narrow; so that it is not easy for the moisture



to flow down through them; while in the case of dwarfs and those whose



heads are abnormally large; the impetus of the evaporation upwards



is excessive。 Those 'on the contrary' whose veins are large are;



thanks to the easy flow through the veins; not addicted to sleep;



unless; indeed; they labour under some other affection which



counteracts 'this easy flow'。 Nor are the 'atrabilious' addicted to



sleep; for in them the inward region is cooled so that the quantity of



evaporation in their case is not great。 For this reason they have



large appetites; though spare and lean; for their bodily condition



is as if they derived no benefit from what they eat。 The dark bile;



too; being itself naturally cold; cools also the nutrient tract; and



the other parts wheresoever such secretion is potentially present



'i。e。 tends to be formed'。



  Hence it is plain from what has been said that sleep is a sort of



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



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