On Sleep And Sleeplessness   

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