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] upwards7, but when it has reached the parts above [becoming cool], it turns back again, and moves downwards8 in a mass. This explains why fits of drowsiness9 are especially apt to come on after meals; for the matter, both the liquid and the corporeal10, 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 repulsed11 the hot, sleep comes on, and the animal so affected12 is presently asleep. A confirmation13 of this appears from considering the things which induce sleep; they all, whether potable or edible14, 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 copious15. It also follows certain forms of fatigue16; for fatigue operates as a solvent17, and the dissolved matter acts, if not cold, like food prior to digestion18. Moreover, some kinds of illness have this same effect; those arising from moist and hot secretions19, 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 infancy21, which is due to the fact that growth predominates in the direction of the former. Hence also they are subject to epileptic seizures22; for sleep is like epilepsy, and, in a sense, actually is a seizure23 of this sort. Accordingly, the beginning of this malady24 takes place with many during sleep, and their subsequent habitual25 seizures occur in sleep, not in waking hours. For when the spirit [evaporation] moves upwards in a volume, on its return downwards it distends26 the veins, and forcibly compresses the passage through which respiration27 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] diluted28 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 intoxicated29, there is ever a large quantity of moisture ascending31. 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 addicted32 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 dwarfs33 and those whose heads are abnormally large, the impetus34 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 counteracts35 [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 derived36 no benefit from what they eat. The dark bile, too, being itself naturally cold, cools also the nutrient37 tract38, and the other parts wheresoever such secretion20 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 recoil39, 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 drowsy40. 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 droop41. 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 onset42 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 replenishment43 cools it by the movement it occasions, so the passages and tracts44 in the head are cooled as the ‘evaporation’ ascends45 thither46? 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 ascend30, 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 erect47 (man alone, among animals, being naturally erect) is withdrawn48; 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 ascended49 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, descends50 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 previously51 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 turbid52 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 chambers53 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 vessels55, called the ‘great’ and the ‘aorta’. It is in the central chamber54 that the [above-mentioned] separation takes place. To go into these matters in detail would, however, be more properly the business of a different treatise56 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, rendering57 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.
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1
analogous
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| adj.相似的；类似的 | |
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2
veins
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| n.纹理；矿脉( vein的名词复数 )；静脉；叶脉；纹理 | |
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3
evaporation
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| n.蒸发，消失 | |
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4
recapitulate
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| v.节述要旨，择要说明 | |
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perceptive
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| adj.知觉的，有洞察力的，感知的 | |
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6
faculty
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| n.才能；学院，系；(学院或系的)全体教学人员 | |
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7
upwards
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| adv.向上，在更高处...以上 | |
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8
downwards
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| adj./adv.向下的（地），下行的（地） | |
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9
drowsiness
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| n.睡意；嗜睡 | |
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10
corporeal
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| adj.肉体的，身体的；物质的 | |
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11
repulsed
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| v.击退( repulse的过去式和过去分词 )；驳斥；拒绝 | |
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12
affected
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| adj.不自然的，假装的 | |
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13
confirmation
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| n.证实，确认，批准 | |
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14
edible
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| n.食品，食物；adj.可食用的 | |
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15
copious
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| adj.丰富的，大量的 | |
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16
fatigue
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| n.疲劳，劳累 | |
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17
solvent
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| n.溶剂；adj.有偿付能力的 | |
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18
digestion
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| n.消化，吸收 | |
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19
secretions
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| n.分泌（物）( secretion的名词复数 ) | |
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20
secretion
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| n.分泌 | |
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21
infancy
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| n.婴儿期；幼年期；初期 | |
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22
seizures
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| n.起获( seizure的名词复数 )；没收；充公；起获的赃物 | |
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23
seizure
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| n.没收；占有；抵押 | |
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24
malady
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| n.病，疾病(通常做比喻) | |
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25
habitual
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| adj.习惯性的；通常的，惯常的 | |
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26
distends
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| v.（使）膨胀，肿胀( distend的第三人称单数 ) | |
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respiration
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| n.呼吸作用；一次呼吸；植物光合作用 | |
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28
diluted
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| 无力的，冲淡的 | |
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intoxicated
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| 喝醉的，极其兴奋的 | |
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30
ascend
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| vi.渐渐上升，升高；vt.攀登，登上 | |
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ascending
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| adj.上升的，向上的 | |
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32
addicted
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| adj.沉溺于....的，对...上瘾的 | |
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33
dwarfs
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| n.侏儒，矮子（dwarf的复数形式）vt.（使）显得矮小（dwarf的第三人称单数形式） | |
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34
impetus
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| n.推动，促进，刺激；推动力 | |
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35
counteracts
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| 对抗，抵消( counteract的第三人称单数 ) | |
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36
derived
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| vi.起源；由来；衍生；导出v.得到( derive的过去式和过去分词 )；（从…中）得到获得；源于；（从…中）提取 | |
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37
nutrient
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| adj.营养的，滋养的；n.营养物，营养品 | |
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38
tract
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| n.传单，小册子，大片(土地或森林) | |
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39
recoil
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| vi.退却，退缩，畏缩 | |
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40
drowsy
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| adj.昏昏欲睡的，令人发困的 | |
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41
droop
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| v.低垂，下垂；凋萎，萎靡 | |
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42
onset
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| n.进攻，袭击，开始，突然开始 | |
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43
replenishment
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| n.补充(货物) | |
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44
tracts
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| 大片土地( tract的名词复数 )； 地带； （体内的）道； （尤指宣扬宗教、伦理或政治的）短文 | |
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45
ascends
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| v.上升，攀登( ascend的第三人称单数 ) | |
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46
thither
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| adv.向那里；adj.在那边的，对岸的 | |
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47
erect
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| n./v.树立，建立，使竖立；adj.直立的，垂直的 | |
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48
withdrawn
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| vt.收回；使退出；vi.撤退，退出 | |
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49
ascended
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| v.上升，攀登( ascend的过去式和过去分词 ) | |
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50
descends
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| v.下来( descend的第三人称单数 )；下去；下降；下斜 | |
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51
previously
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| adv.以前，先前（地） | |
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52
turbid
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| adj.混浊的，泥水的，浓的 | |
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53
chambers
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| n.房间( chamber的名词复数 )；（议会的）议院；卧室；会议厅 | |
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54
chamber
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| n.房间，寝室；会议厅；议院；会所 | |
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55
vessels
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| n.血管( vessel的名词复数 )；船；容器；（具有特殊品质或接受特殊品质的）人 | |
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56
treatise
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| n.专著；(专题)论文 | |
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57
rendering
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| n.表现，描写 | |
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