Heart, brain, blood, pneuma 133
through the mouth, as is likely. For the air, passing through the vessels, itself rises
and brings up with it the thinnest part of the blood. The moisture mixing with the
air becomes white, for the air being pure is seen through thin membranes. For this
reason the foam appears completely white. When then will the victims of this dis-
ease rid themselves of their disorder and the storm that attends it? When the body
exercised by its exertions has warmed the blood, and the blood thoroughly warmed
has warmed the breaths, and these thoroughly warmed are dispersed, breaking up
the congestion of the blood, some go out along with the respiration, others with
the phlegm. The disease finally ends when the foam has frothed itself away, the
blood has re-established itself, and calm has arisen in the body.^33
The structure of this explanation is very similar to the one found inOn
the Sacred Disease, yet there is a significant difference: air is not obstructed
in its course, but air itself is the obstructing factor. Air causes the blood
to become chilled, it flows more slowly and therefore it is less capable of
providing the body with ‘consciousness’. Another interesting factor is the
comparison with sleep: a non-pathological state is employed to illustrate a
more serious disorder resulting from the same physiological mechanism.^34
The association with sleep returns in Aristotle, who dwells briefly on
the subject of epilepsy in his treatiseOn Sleep and Waking(De somno et
vigilia, Somn. vig.). Aristotle considers sleep a form of epilepsy, albeit not a
pathological one. Sleep is a result of the digestion of food: after consumption
food is carried to the centre of the body and ‘cooked’ or digested by the
heat of the heart. The process of cooking gives rise to the evaporation
(anathumiasis) of food; the air (pneuma), saturated by these hot vapours, is
carried upwards from the heart to the brain and causes the head to become
heavy. The brain causes these vapours to be chilled and return to the heart.
Thus the heart is chilled, which is what actually causes the sensory faculties
to fail (the ‘formal cause’, i.e. the definition of sleeping).^35
Sleep arises from the evaporation due to food... Young children sleep deeply,
because all the food is borne upwards. An indication of this is that in early youth
the upper parts of the body are larger in comparison with the lower, which is due
to the fact that growth takes place in the upward direction. Hence too they are
liable to epilepsy, for sleep is like epilepsy; indeed, in a sense, sleep is a type
of epileptic fit. This is why in many people epilepsy begins in sleep, and they
are regularly seized with it when asleep, but not when awake. For when a large
amount of vapour is borne upwards and subsequently descends again, it causes
the blood vessels to swell and it obstructs the passage through which respiration
passes. (Somn. vig. 457 a 4 – 11 )
(^33) On Breaths 14. 1 – 4 ( 6. 110 – 12 L.), tr. Jones in Jones and Withington ( 1923 – 31 ) vol.ii, modified.
(^34) For the ambivalent status of sleep in ancient medicine see Debru ( 1982 ) 30.
(^35) For precise details of this process see Wiesner ( 1978 ) 241 – 80.