Heart, brain, blood, pneuma 129
does not prevent him from repeatedly speaking of ‘experiences typical to
the soul’, activities a human being carries out ‘with his soul’, or perceptions
which ‘penetrate the soul’. According to Aristotle, the functioning of the
dual entity that body and soul constitute is governed by a large number of
organs and material factors. The heart is assigned the role of ‘beginning’ or
‘origin’ (arche ̄), both as a source of essential bodily heat (required among
other things for the digestion of food) and as the seat of the central sense
organ, which is connected with the limbs and the separate sense organs and
co-ordinates the data it receives from them.^21 Furthermore, in exercising
this co-ordinating task the heart is supported by the blood (as a medium
for transporting sensory information) and air (pneuma, for the transmis-
sion of motor signals). Their role is important, yet not fully defined.^22 The
size of the heart, which differs in each species of animal, has an influence
on certain character traits and on susceptibility to certain emotions;^23 the
condition of the blood (pure, turbid, cold, hot) influences the quality and
speed of sense perception.^24 The brain is not involved in all this: it has no
cognitive faculties and serves only as a chilling element in the body, for
tempering the heat that radiates from the heart.^25
An even more elaborate physiological theory is presented by Diocles of
Carystus (fourth centurybce). He assumes interaction between the heart
(to him the real seat of the mind), the brain (which plays a pivotal role in
sense perception) and the so-called ‘psychicpneuma’, a delicate substance
that is responsible for transmitting sensory and motor signals.^26
It is clear, then, that many medical authors of the fifth and fourth cen-
turiesbceassume a cognitive centre somewhere in the body from where
abilities such as perception and movement are ‘transported’ or ‘transferred’
to peripheral organs. Organs for perception, limbs and other parts of the
body are assumed to be connected to each other and to a centre via cer-
tain ‘passages’ (poroi,phlebes,neura).^27 Through these passages air or blood
are conducted; an accumulation of certain bodily fluids (such as phlegm
or bile) can cause the passages to get blocked. The assumption of the
existence of this network of passages and the ideas about their course and
ramifications are highly speculative and hardly based on what we would
(^21) On Youth and Old Age(De iuventute et senectute, De iuv.) 468 b 32 ff.
(^22) There is much debate on the question whether it is the blood orpneumawhich, according to
Aristotle, carries sensory information in the body. A summary and standpoint can be found in van
der Eijk ( 1994 ) 81 – 7.
(^23) Part. an. 667 a 10 – 20. (^24) Part. an. 656 b 5 ; 648 a 2 ff.; 650 b 19 ff.
(^25) Part. an. 2. 7. (^26) Diocles, frs. 78 and 80 vdE.
(^27) In this respect it should be noted that nerves were not discovered until after Aristotle, in third-century
Alexandria.