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The nervous system in antiquity

This overview of the nervous system in antiquity shows that whereas neuro-anatomy had its heyday in the 4th and
3rd centuries BC (the Alexandrian School) and was later consolidated by Galen in the 2nd century AD, neurophysiology
remained largely mired in erroneous concepts. While the  descriptions of neurological disease often produced quite
apt clinical pictures, poor understanding of pathophysiology  resulted in ineffectual therapy. The embryonic origins of
modern neurology lie in the gradual evolution of neuroanatomy  and neurophysiology in antiquity. Closely allied
to the early understanding of the nervous system was the  contested issue of where the control centre of the body
(hegemonikon) was located. These are the issues that we review.

The body’s control centre
The need to place all actions of the body under the control of  a single centre or principle (hegemonikon – a term coined by
the Stoics) was pervasive in Western antiquity.1 Although the  head (brain) was favoured by many, entities such as the chest,
heart, liver, blood and the pneuma (‘vital spirit’) also had their  supporters. Hippocrates stated that the diaphragm, which was
favoured by some, could not be seriously considered because it did not contain a cavity2 (presumably to house the soul or ‘vital
spirit’).
In Ancient Egypt, the heart was considered to be the chief  organ of the body. The brain was viewed as being of little
importance – at best, the producer of mucus during illness,subsequently discharged through the nose.3,4 In Mesopotamia,
the liver was thought to be the seat of the soul.5 In Greece,the so-called Presocratic philosopher-physicians (6th and 5th
centuries BC) laid the foundation of empirical science that led  to the Hippocratic era. Alcmaeon of Croton, a contemporary
of Pythagoras, favoured the head (and brain), as did Diogenes  and Democritus.6 Parmenides6 and the influential Sicilian,
Empedocles,1 however, thought that the soul was seated in the  thorax or the blood surrounding the heart.

The Hippocratic Corpus (mainly 5th and 4th centuries BC)
presented divergent views. In The Sacred Disease (chapter 19),the brain is called the centre of bodily functions but, in a later
text (The Heart, chapter 7), the left ventricle of the heart is the  seat of the soul. In Diseases Book II, higher bodily functions are
ascribed to both the heart and the brain.
While Plato favoured the head, Aristotle placed the  hegemonikon in the heart, stating that a bloodless brain could
not house the soul. During the 4th century BC, the Stoics,Epicurians, Praxagoras and Diocles all nominated the heart,
while Strato placed the seat of the soul between the eyebrows.
At the onset of the Hellenistic era (late 4th century BC), the  cardiocentric consensus (heart as control centre) gradually
receded, as influential Alexandrians such as Herophilus  and Erasistratus brought evidence of an encephalocentric 
hegemonikon.1 Erasistratus thought it might be located in the  meninges rather than the brain.1 Chrysippus (3rd century
BC), however, still favoured the heart,7 while Asclepiades (1st  century BC) taught that there was no hegemonikon, since the
senses controlled all bodily activities.1
In the Roman era, influential figures such as Galen1and Rufus (2nd century AD)7 strongly defended the
encephalocentric approach, but Lucretius (1st century BC)  and Alexander of Aphrodisias (2nd century AD)1 were
cardiocentrists, defending a point of view that persisted  through medieval times and was still reflected by Shakespeare
in his play The Merchant of Venice (III.ii.63): ‘Tell me where is  fancy bred, or in the heart, or in the head’?8
Phrases such as ‘heart and soul’, ‘with all my heart’ and  ‘heartfelt grief’ have their origin in the cardiocentric view of
the past.

Neuro-anatomy
In Ancient Egypt, the brain was considered unimportant and  there was no real knowledge of the nervous system. During the
mummification process, the brain was destroyed and removed  via the nose and through the cribriform plate.3 But in the
Edmund Smith Papyrus, the brain is identified as an organ,4and limited neuro-anatomical features such as the meninges,
cerebrospinal fluid, surface blood vessels and convolutions,which were observed through open skull wounds, are  mentioned.3 Similarly, Mesopotamian writings reveal no  significant neurological knowledge.7

Greece (Classical era)
In pre-Hippocratic times, the philosopher-physician Alcmaeon  of Croton (6th century BC) probably took the first tentative
steps towards exploring the brain and nervous system. He  possibly dissected animals, and was said to have examined an
excised human eye. He linked the senses functionally to the  brain and postulated passages connecting the eyes, ears, nose
and tongue (taste) with the brain. He might have described the  optic nerve.1
The Hippocratic Corpus (the foundation document of  empirical medicine) contains little on neuro-anatomy,
knowledge of which was gained from general observation and  limited animal (but no human) dissection.1 Two membranes
covering the brain (the dura and pia mater, but not the  arachnoid) were described; these membranes partially divide
the brain down the middle into the right and left hemispheres.
Apparently based on dissection of the goat, the brain was said  to be oedematous and foul-smelling.1,2 The spinal cord was
described as attached to the brain and of the same consistency,differing from that of bone marrow. The fluid under the brain
membranes (meninges) was found to be confluent with that  covering the spinal cord.9 Passages through the skull and
meninges linking the eyes and ears to the brain were noted,but no such passage to the nose. Blood vessels, ducts and
nerves were confused – phlebes were described as hollow  tubes carrying various fluids, and neura were solid structures
(including nerves, tendons and ligaments). Semen was believed  to originate in the head and to be conveyed in neura. The eye
was thought to consist of three tunics (sclera, choroid and  retina) and to be nourished by the brain through the hollow
optic nerve.9
Although not medically trained, Aristotle (4th century BC)  performed extensive animal dissections and confirmed that
the main brain consisted of two hemispheres. He described  a lesser brain (parenkephalon (cerebellum)) behind the main
brain (encephalon (cerebrum)). The brain was thought to be  covered by two meninges and to contain few blood vessels. He
also found that some animals had small cavities (ventricles) in the cerebrum, and mentioned the presence of a few nerves
originating in the brain (cranial nerves).1 The concept of the  neuron still included tendons and ligaments besides nerves.
He reported that men had larger brains than women and that,relative to body size, man had the largest brain of all creatures.7
Praxagoras (4th century BC) claimed that blood vessels  terminated as nerves, so supporting the argument that the heart
was the central controlling organ.7 He and Philotimus believed  that the brain was merely an outgrowth of the spinal cord.1
Vindicianus later wrote that Diocles (4th century BC, sometimes  called the second Hippocrates) had said that the right half of
the brain controlled sensation and the left side, intelligence.10

Alexandria (Hellenistic era)
Up to the Hellenistic era, all knowledge of neuro-anatomy   had been based purely on animal dissections. The heyday of
neuro-anatomy dawned when Herophilus and Erasistratus  commenced human dissection (probably even vivisection)
of condemned criminals, under patronage of the Ptolemaic pharaohs in the newly established city of Alexandria (332
BC). However, with the probable exception of Eudemus (3rd  century BC), Numisianus and Marinus (2nd century BC),
subsequent Alexandrian physicians did not continue systematic  human dissection.1 Virtually all the extensive original writings
of Herophilus and Erasistratus were destroyed, and our  knowledge of their contributions is based on comments by later
authors such as Theophilus, Oribasius, Rufus, Vindicianus and  – in particular – Galen.6 Herophilus and Erasistratus probably
dissected as many, or more, animals than humans, which is  indicated by occasional errors in their reported findings, e.g.
the description of the presence of a rete mirabilis anastomosis at  the base of the human brain – a structure found in angulated
animals but not in humans. But it can be stated confidently  that the basis of human neuro-anatomy was laid by the two
Alexandrians.1 Illustrations were used for the first time in  history to clarify descriptions, a technique later disapproved of
by Galen.8 Both performed vivisection on animals (and possibly  humans) to verify the function of parts of the brain and nerves.
Herophilus’ impressive findings included the following:6,10

1. A description of skull sutures.
2. Two layers of meninges (the dura mater and pia mater)  covering the brain, the outer one involved in the formation
of the tentorium cerebelli, and lining the intracranial venous  sinuses. This included the prominent junction of sinuses
named the lênos (wine vat) (Galen renamed it the torcular  Herophili; however, this structure is rarely prominent in
man, and the term could represent another example of  animal anatomy corrupting knowledge of human anatomy).
3. Differentiation between the cerebrum and cerebellum.
Herophilus considered the latter to be responsible for motor  activity and equilibrium.
4. The 2 lateral brain ventricles, their openings into the 3rd  ventricle, aqueduct of the midbrain and the 4th ventricle,
and the choroid plexus (resembling the fetal choroid  membrane) lining these spaces.
5. The 4th ventricle was considered to be the seat of the soul,and details such as a pen-like cavity in its floor (calamus
scriptorius – probably the aperture into the spinal column)  were described.
6. The origin of the spinal column from the brain, the pineal  body (resembling a pine cone), the structure of the eye and
at least some of the cranial nerves (optic with optic chiasma,oculomotor, trigeminal, facial, auditory and hypoglossal
nerves) were identified.

7. His detailed study of nerves (distinguishing between motor  and sensory nerves) was a fundamental contribution.
However, he still considered the optic nerve to be hollow,and included tendons and ligaments as terminal extensions
of nerves in muscles (this part of the complex mechanism  then supposedly enabling voluntary motor activity).

We know more about Erasistratus’ neurological concepts  as he was quoted more extensively by Galen (often critically)
because he dared to differ from Hippocrates.7 Largely  agreeing with Herophilus’ neuro-anatomy, he taught that the
brain’s convolutions related to mental ability (therefore more  convolutions in man than in animals, and in the cerebellum
rather than the cerebrum). He claimed that not only the optic  nerve but all sensory nerves were hollow to enable the flow of
‘psychic pneuma’ (see below); sensory nerves originated in the  meninges and motor nerves in the brain.1,6
Marinus (2nd century BC) made a detailed study of the  cranial nerves, describing the olfactory nerve structure, and a
large nerve descending from the lower brain into the thorax  (either the vagus or recurrent laryngeal nerve).6

Roman era
With human dissection virtually discontinued in Hellenistic  times, the subsequent Roman era brought little enhancement
of human neuro-anatomical knowledge. At the turn of the  1st century AD, Rufus of Ephesus reviewed known medical
information and, although misconception regarding the neuron  persisted, he elegantly described the brain, spinal cord and
nerves as an interconnected nervous system.7
Galen (2nd century AD), the most prominent physician of  Roman times, whose views became dogma in the medieval
era, wrote extensively on medical matters, including the  nervous system. His views on neuro-anatomy were based on
existing knowledge (mainly the Alexandrian findings) as well  as extensive personal dissection of animals (oxen and apes in
particular) but not humans. He largely confirmed the work  of Herophilus and most of that of Erasistratus. Until then, the
ventricles had been much studied, the brain substance being  seen as little more than supporting tissue. Galen now described
the corpus callosum, thalamus, septum lucidum (separating the  lateral ventricles), and the fornix in the roof of the 4th ventricle
– the latter he accepted as the centre of the hegemonikon. The  pituitary gland and its stalk attached to the 3rd ventricle floor
were described; like Herophilus, he wrongly placed a retiform  plexus at the base of the human brain.1
Galen gave a good description of the blood vessels of the  brain. The optic nerve and most (but not all) other nerves
were believed to be hollow. The spinal cord was said to be a  bundle of nerves running together from the brain down the
vertebral column to the rest of the body and emerging from its  bony cage through intervertebral foramina. He still considered
ligaments and tendons as equivalents of nerves, and stated that  while sensory nerves were soft and arose from the cerebrum,motor nerves arose from the spinal cord and were hard; nerves  arising from the junctional area could be either soft or hard. He was adamant that brain convolutions had no qualitative  relationship to brain function.7,11
Post-Galenic writers of antiquity (e.g. Oribasius) quoted their  predecessors without adding significant new knowledge.5

Neurophysiology
Pneuma
Neurophysiological hypotheses largely revolved around  concepts regarding the nature and function of pneuma (air) as
‘vital spirit’ essential for life, which entered the body mainly  during breathing but also through pores in the skin. Originally
postulated by Anaximenes (6th century BC),1 the concept  was supported by Democritus who taught that pneuma was
transmitted by semen.12 Diogenes’ view (that pneuma was  breathed in with air and transmitted through the body in blood
vessels as well as other ill-defined passages, enabling cognition  and intelligence) became widely accepted.1 The Hippocratic
Corpus described pneuma as a major enabling factor in brain  function, entering the brain through blood vessels, but also
directly via pneumatic channels from the mouth and nose.2
Aristotle stated that, as the central controlling organ of the  body, the heart (through ‘innate heat’) converted pneuma (in
blood) to ‘connate pneuma’, which was the ‘generative heat’  in semen, but also enabled organs to experience sensation.
In view of its considered bloodlessness, the brain was  therefore unimportant in this process. Its main role was seen
as thermoregulatory – keeping the body cool. Although  Praxagoras referred to ‘psychic pneuma’, this important concept
was first formulated by Diogenes (4th century BC) who, as  promoter of the heart as seat of the hegemonikon, claimed
that ‘psychic pneuma’, formed in the heart, spread through  the body’s vessels to effect voluntary motion. Interruption
of this flow resulted in disease. The Stoics made a major  contribution to the pneuma theory by stating that it was a
multifaceted changeable force, capable of inter alia becoming  ‘vital pneuma’ (the soul itself) or ‘psychic pneuma’ (responsible
for consciousness and intelligence). The brain played no direct  role in all this.1
Erasistratus taught that ‘psychic pneuma’, converted from  ordinary pneuma in the meninges, was the vital force necessary
for nervous function.1 Herophilus apparently believed that  ‘psychic pneuma’ was formed in the choroid plexus of the lateral
ventricles (out of ‘natural pneuma’) from where it permeated  through to the 4th ventricle (command centre) and activated all
nerve action (there being a ‘sensory pneuma’ for sensory nerves,and ‘motor pneuma’ for motor nerves). Praxagoras’ hypothesis
was that voluntary and involuntary movement, spasms,palpitations and tremors were due to arterial (not nervous)
activities. Galen’s views, which remained in vogue for the next  millennium, represented a further evolutionary development,which stated that a ‘pneuma-like substance’ absorbed in the lungs reached the heart where, under influence of ‘innate
heat’, it converted to ‘vital pneuma’, which passed to all organs  via the arteries. On reaching the brain, this was converted to
‘psychic pneuma’ in the retiform plexus or choroid plexus in  the lateral ventricles. ‘Psychic pneuma’ could also be formed in
the brain ventricles from pneuma absorbed directly through the  nose (and cribriform plates). ‘Psychic pneuma’ then permeated
the ventricular system and the cerebellum in particular,activating nerves by flowing through them; it also passed via
the optic nerve to the eye. The role of pneuma in interaction  with the soul or activation of neuro-psychiatric functions was
not elaborated on by Galen.6,8

Other mechanisms
The popular hypothesis of antiquity (that health was  dependent on an equilibrium between body humours and
basic elements) also held for neurophysiology. Scarborough13  suggests that the concept of four humours (blood, phlegm,
yellow and black bile) probably originated with Thales   (early 6th century BC), while Alcmaeon first stressed the
importance of an internal equilibrium of natural phenomena.10
Empedocles added four basic elements (water, fire, earth and  air)12 and Philistion ascribed four qualities (hot, cold, dry
and moist) to these elements.10 Disease would then result  from internal imbalances, which in turn could be caused by
external factors (such as excessive variation in temperature  or humidity, trauma, incorrect diet or physical activity) or the
blockage of passages that conveyed the humours and elements.
Hippocrates’ consolidation of these theories remained dogma  throughout antiquity, although the early Alexandrians
disagreed with mainly the humoural theories.14
Aristotle believed that the brain’s main function was that of  cooling the body and the hot heart in particular.1 Hippocrates
stated that the spinal cord was indeed warmer than the brain,1and Galen confirmed the brain’s supposed cooling function.7
Plato maintained that the brain was the body’s controlling  organ, and that the soul consisted of three parts – the main
or rational soul was in the brain, but the heart and upper  abdomen also housed components.7

Neurological illness
Although the symptoms and signs of disease were often quite  well described, ignorance about relevant pathophysiology  barred the ancients from prescribing effective therapy.
Recognisable neurological illnesses included the following:
Papyri from ancient Egypt mention unilateral facial palsy  which could be Bell’s paralysis, unilateral headache possibly
compatible with migraine, and a variety of paralyses caused  by cranio-spinal injury.3 The Hippocratic Corpus devotes a
book to epilepsy (The Sacred Disease), clearly describing variants  of the disease.2 Erasistratus recognised apoplexy1 and, 800
years later, Caelius Aurelianus differentiated it from epilepsy,hysterical conditions, ‘paralysis’ and ‘general lethargy’. The
latter two conditions clearly represented a hodge-podge of illunderstood  neurological problems which, like most illnesses,
were blamed on disequilibrium within people or abnormal  pneuma.16 Head wounds received prominent attention but there
was limited comment on neurological complications, although  Hippocrates did describe contralateral convulsions.17 Headache
was recognised as a complex symptom associated with many  diseases,18 and Hippocrates attributed mental disease to
derangement of the brain.2 In the 1st century AD, Celsus19  recognised four kinds of insanity: melancholia, progressive
‘foolishness of the spirit’ (possibly dementia), illusions in an  otherwise healthy person, and ‘phrenitis’ (delirium associated
with fever). Hydrophobia (rabies), first described in Hellenistic  times, was clearly defined by Caelius Aurelianus.16

François P Retief, Louise Cilliers

François Retief is former Dean of the Medical School of the  University of the Free State and Rector of MEDUNSA. He has
retired as Rector of the University of the Free State, where he is  currently a Research Fellow.
Louise Cilliers is Senior Professor and Head of Classical  Languages at the University of the Free State, and Editor of Acta Classica.

NOTES

1. Rocca J. Galen on the Brain. Leiden: Brill, 2003: 17-63, 77-188, 254-356.
2. Hippocrates. The Sacred Disease, ch 6: 17-19.
3. Nunn JF. Ancient Egyptian Medicine. Norman: University of Oklahoma Press, 1996: 43-93, 179.
4. Sigerist HE. A History of Medicine. Vol. I. New York: Oxford University Press, 1955: 353.
5. Major RH. A History of Medicine. Springfield: Charles Thomas Publishers, 1954: 31, 200-211.
6. Von Staden H. Herophilus. Cambridge: Cambridge University Press, 1989: 159-206, 248, 314.
7. Clark E, O’Malley CD. The Human Brain and Spinal Cord. Berkeley: University of California
Press, 1968: 1-18, 141-150.
8. Clarke E, Dewhurst K. An Illustrated History of Brain Function. Oxford: Sandford Publishers,
1972: 2-8.
9. Hippocrates. Places in Man, 2.1-3, 3.5, 4.0, 10.2, 32.1.
10. Longrigg J. Greek Medicine from the Heroic to the Hellenistic Age. London: Duckworth, 1988: 69,
76, 86-88, 107.
11. Singer C. Galen on Anatomical Procedures. Oxford: Oxford University Press, 1956: 234-236.
12. Nutton V. Ancient Medicine. London: Routledge, 2004: 45-55, 92-93, 121-122, 179.
13. Scarborough J. Medical and Biological Terminologies. Norman: University Oklahoma Press,
1992: 216.
14. Smith WD. Erasistratus’ dietetic medicine. Bull Hist Med 1982; 56: 378-409.
15. Hippocrates. On Diseases II. p.5.
16. Caelius Aurelianus. Acute and Chronic Diseases. Drabkin IE (translator). Chicago: University of
Chicago Press, 1950: chapters 4-137.
17. Hippocrates. Injuries of the Head, ch. 19, 21.
18. Caelius Aurelianus. Acute and Chronic Diseases. Drabkin IE (translator). Chicago: University of
Chicago Press, 1950: chapters 4-183.
19. Celsus. De medicina III, 18.3-19.

SOURCE  http://www.samj.org.za

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