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Brain (2008), 131, 2798 ^2801
BOOK REVIE W
Cicero’s brain and vibrating nerves
Few pairs of books about the history of the brain could be
more discordant than this one. Daniel Lord Smail, a
Harvard historian, makes a strong plea for integrating the
general history of mankind with the evolutionary history of
the brain. No mean task, certainly not for someone whose
first book, published in 1999, examined changes in spatial
designation in the notarial registries of medieval Marseille.
The other book, edited by Whitaker, Smith and Finger,
contains a collection of essays about 18th century advances
in understanding of the nervous system. Despite their
disparate vantage points, the pairing serves as a reminder
that the organ of neuroscience is not immutable but
evolving—however slowly.
The first three chapters of Smail’s book are a passionate
vindication of ‘deep history’, that is, history beginning at least
with the emergence of Homo sapiens sapiens in Africa, some
140 000 years ago. In his eyes, the ‘prehistoric’ era should not
be left to geologists, anthropologists and archaeologists.
When Palaeolithic tribes migrated to Europe and Asia, some
85 000 to 50 000 years ago, humans were still migrant hunters,
with an economy ‘based on the calorie’. Probably it was by
sheer necessity—prey having become scarce—that around
10 000 years ago the nomadic way of life gave way to a
sedentary, agricultural society: the Neolithicum or late Stone
Age. Remarkably, this transition took place at roughly the
same time in different continents.
Most historians, however, limit their narrative to history
since the Bronze Age, 5500 years before our time, when also
nation states developed. Smail chides his colleagues for their
‘myopic view’ and ‘sterile presentism’, hardly disturbed by the
time revolution of the 1860s articulated in Darwin’s ‘On the
origin of species’ (1859), Lyell’s ‘The geological evidences of
the antiquity of man’ (1863) and Lubbock’s ‘Pre-historic
times’ (1865). The habit of starting history with Mesopotamia
(or with Egyptian culture, popular in the 19th century) he
regards as a lame substitute for the traditional biblical
signposts: the Garden of Eden, the deluge or the destruction
of the Tower of Babel.
Smail punctiliously and eloquently dissects the resistance of
historians against inclusion of the Stone Age in regular
history. Their most common argument, of course, is the lack
of written records. For that reason the ‘speechless past’ is often
regarded as a stagnant buffer zone, before ‘true history’ began.
But other disciplines have adopted a broader definition of
ON DEEP HISTORY
AND THE BRAIN.
By Daniel Lord Smail
2008.
Berkeley: University of
California Press
Price: £12.95
ISBN: 978-0-520-25289-9
BRAIN, MIND AND
MEDICINE – ESSAYS IN
EIGHTEENTH-CENTURY
NEUROSCIENCE.
Edited by Harry Whitaker,
C. U. M. Smith and
Stanley Finger.
2007.
New York: Springer
Price: $36.00
ISBN: 978-0-387-70966-6
‘documents’: lumps of rock, fossils, mitochondrial DNA,
isotopes, behavioural patterns, potsherds, phonemes and cave
paintings. Spoken language, not written language, should be
the defining characteristic of mankind, one that may well have
been present in earlier hominins than H. sapiens sapiens.
A more complex argument for the tradition of setting ‘prehistory’ apart is the assumption that history should
take account only of the period characterized by
ß The Author (2008). Published by Oxford University Press on behalf of the Guarantors of Brain. All rights reserved. For Permissions, please email: [email protected]
Book Review
‘cultural evolution’, the transmission of rites and knowledge
to subsequent generations. Darwinian evolution is biology,
not history, as the reasoning has it. Smail disagrees and argues
that it is impossible to attach a date to the point of rupture
where Darwinian selection would have been replaced by
cultural transmission. That he designates cultural evolution as
‘(neo)Lamarckian’ is a little confusing, since intergenerational
transmission occurs exclusively by learning and relearning
and not by biological transmission of acquired traits, as
Lamarck (1744–1829) would have it.
In the pivotal fourth chapter, ‘The new neurohistory’,
enters the brain centre-stage. Smail starts from two
premises. First, cultural factors not only heavily influence
behaviour, but may even become ‘hardwired’ into the brain.
Second, genetic influences on behaviour should not be
simplified as ‘one gene, one behavioural trait’, as in the
‘gene for blue eyes’, but rather as determining a multitude
of ‘behavioural modules’, engineered by natural selection.
These modules may or may not be expressed, depending on
the environment. They may also be used for ends other
than those best served at the time the original adaptive trait
emerged by natural selection. In that case, traits are termed
‘exaptations’, a concept proposed by Stephen Jay Gould: in
the same way that the nose can be used to perch spectacles
on, a given brain module can be used to play chess. Smail
then outlines the traditional viewpoint of evolutionary
psychology, which has it that the 140 000 year history of
hominins is too short to have influenced behavioural
modules; that our brains are more suited to the East
African savannahs than to industrialized society; and that
human civilization entirely results from cultural, not
biological evolution. As Sir Peter Medawar once put it:
‘We could return to the Stone Age in one generation’
(Medawar 1982). Ancient instincts from this ‘evolutionary
hangover’ can still be identified, such fear of the dark,
males being attracted to females younger than their actual
partner and aversion to mating with persons one grew up
with, even if they are unrelated.
But subsequently Smail delicately dismantles the position
that civilization put an end to biology. The persistence of
behavioural ‘fossils’ depends on conjectural backward
reasoning, all domesticated animals having undergone
remarkable transformations in less than 10 000 years. The
ability of most humans to synthesize lactase and the
protection against malaria provided by the sickle-cell trait
testify to the occurrence of gene-culture co-evolution. The
genetic diversity (polymorphisms) within each ‘race’ and
sex posits against stability. And, finally, human society may
well be an equally valid source of selection pressure as the
classical predator-prey relationship (an ‘evolutionary armsrace’ with a single species). ‘Substantial changes could have
taken place in the human genome since the time of the
Roman Empire’, Smail wagers. In other words, Churchill’s
brain may well have differed substantially from Cicero’s!
The last chapter is a sobering dissection of recent cultural
evolution, in which the author argues that, from the 18th
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century onwards through pressures of political and religious dominance and subservience, secretion of nerve
transmitters has to some extent been replaced by a ‘dizzying
array of mood-altering practices and substances’, from
amusement (‘teletropy’) to gossip or cocaine (‘autotropy’).
Overall, the text is elegantly written as well as accessible:
lapses into historical jargon are few and far between. Apt
metaphors reflect digestion of a wealth of knowledge about
biology and evolution. The notes have been relegated to the
back of the book, integrated with an impressive bibliography, while the index is excellent.
Eighteenth century Europe inspires Smail to write:
‘. . . with its caffeinated culture, its sentimental novels and
pornographic works, and its growing array of consumer
goods, [it] provides a gold mine of case studies that could
benefit from the adoption of neurohistorical perspectives’.
The book edited by Whitaker, Smith and Finger, however,
addresses cultural, not biological evolution. Indeed, the
18th century represents a crucial episode in history—to a
large extent coinciding with the Enlightenment. That simple
term represents a huge and multi-faceted transformation of
society in general, in which the traditional authority of
aristocrats and ecclesiasts was challenged by an emerging
middle class, hungry not only for power, sometimes even
revolution, but also for knowledge. The intellectual climate
changed accordingly. Aristotelian views of the world and its
inhabitants as an unmovable and coherent system, adorned
with a Christian varnish by Thomas of Aquino and other
church fathers, were gradually replaced by the urge to
unravel the secrets of the natural world. The humanistic
outlook of the philosophical vanguard verged on atheism
(Israel, 2001), while local tongues replaced Latin as the
language of science; human rights were to some extent
bought at the price of a return to provincialism, one might
say. And in medical thinking the body moved to the centre
of attention, at the expense of the soul (Porter, 2003). The
inevitable conflicts raged even within the minds of pioneers
and caused Swammerdam and Stensen to return to the
safe haven of religion; Stensen ended his life as a bishop
in Rome.
Diseases had until then been traditionally explained in
humoral terms. Naturally, the Renaissance had prompted
changes in Hippocratic and Galenic models of disease as a
specific disturbance of the delicate equilibrium between
essential body humours. Chemical and physical principles
were included, such as fermentation, acid–base equilibrium
and early particle theory. Nevertheless, the perception of
normal and disturbed body functions remained essentially
‘fluidist’ until introduction of systematic post-mortem
studies in the 18th century identified changes in defined
organs as the substrate as well as the cause of disease. From
then on medicine became ‘solidist’. Morgagni (1682–1771)
rightly stands out as the father of pathological anatomy, by
dint of his monumental book ‘De sedibus et causis
morborum’ (‘about the seats and causes of diseases’),
summarizing a lifetime’s experience of autopsy studies,
2800
Brain (2008), 131, 2798 ^2801
mostly performed in Padua. Of course change was in
the air in 1671, when—in his 80th year—Morgagni’s
work appeared. Yet the apparently simple term ‘seats’
encapsulates the immense paradigm shift that overturned
medicine in the 18th century, from a ‘systems approach’ to
an ‘organ-based approach’. From organs the attention
would shift to tissues, from tissues to cells, from cells to
DNA, and from DNA to proteomics. This is where the
reductionist trajectory ends today, leaving us short-sightedly
wondering how to reconstruct the system from a mass of
details. But that is another story.
The transformation of physiological and medical thinking
in the 18th century forms the backdrop against which new
ideas about the function of the nervous system emerged. In
the multi-author book by Whitaker and colleagues that
decor is alluded to but not explained, apart from a single
chapter about the Gentlemen’s Magazine, which exemplifies
the dissemination of knowledge across the middle classes.
Most developments in neuroscience are distributed over the
other 24 chapters. The editors have been rather liberal in
their time scale, conveniently extending the ‘long 18th
century’ from 1664 (Thomas Willis’ ‘De Cerebri Anatome’)
to the 1840s (Emil Du Bois Reymond’s discovery of the
action potential). The attempt to arrange the different
contributions in a more or less thematic fashion has been
only partly successful, as the chosen themes are somewhat
nebulous, inviting overlap: ‘introduction’ (fine, with an
excellent ‘neurocalendar’), ‘background’ (with surprisingly
little about society, science or even medicine in general),
‘the nervous system’, ‘brain and behaviour’, ‘medical
theories and applications’ and finally ‘cultural consequences’. Also the editorial introductions to each of the
resulting six sections read more like summaries than
syntheses. Although the information contained in the
book is priceless, readers are left with the task of
reconstructing the overall image for themselves. On the
other hand, by choosing such an eclectic approach, the
editors have remained true to their subject, since compilation as a manner of presenting facts is a hallmark of the
Enlightenment. In that era reading became an active rather
than a passive process, according to the inductive view that
an encyclopaedic collection of separate, accurate observations would necessarily lead to the emergence of more
general rules.
Let me, then, try to paint the overall picture. The three
conceptual leaps, more or less in consecutive order, as I
would prefer to distinguish them in the growing body of
knowledge concerning the nervous system in the 18th
century, are: first, the notion that the cerebral substance
and not the cerebrospinal fluid is the substrate of sensation,
motion and cognition; second, that nerves conduct signals
not by means of fluid or mechanical impulses, but through
some mysterious ‘change’ and the ‘energy’ for inducing
movement, sensation and thought resides only in the
central nervous system, not in muscles or other peripheral
tissues; and third, electricity proves to be the elusive force
Book Review
underlying the signalling process. Of course the story does
not end there. But electrophysiology and localization of
some defined functions in the brain are typically 19th and
20th century issues, while the problems of charting the
innumerable networks and understanding consciousness
still remain to be solved.
The question of brain substance versus brain fluid as the
substrate of mental activity receives surprisingly little
attention in the book. True, conventional chronology has
it that the ancient Greek notion of the cerebral ventricles as
the seat of the mind was superseded by the middle of the
17th century, to a large extent through the teachings and
writings of Sylvius De la Boë in Leiden and Willis in
Oxford (Clarke and Dewhurst, 1996). But the analogy
between blood as the life force of the body and
cerebrospinal fluid as the medium of thought was too
powerful to be dispelled overnight. Rene Descartes, whose
‘De homine’ was written in the 1630s but appeared only
post-humously, in 1662, attributed a central role to
cerebrospinal fluid as the medium through which signals
are transmitted from the pineal gland to pores in the brain
mantle and vice versa. Similar views lingered until the very
end of the 18th century, which saw the publication of
Sömmerring’s ‘Das organ der Seele’ (1796), a work that
surprisingly receives no mention from Whitaker and
colleagues. Sömmerring’s famous and accurate illustration
of a sagittal section of the brain is accompanied by a
multitude of citations leading him to conclude that the
brain substance only serves to interact with the cerebrospinal fluid, which is the true ‘organ of mind’. The
monograph closes with an epilogue by an aged Immanuel
Kant (1724–1804), who wisely prefers to remain on the
fence.
Even though ‘solidist’ views on brain function largely
prevailed in the 18th century, brain fluid was for a long
time still held responsible for the transmission of signals
through nerves. Of course this required nerves to be hollow,
a view to which both Descartes and Willis subscribed. That
sectioned nerves failed to show a lumen only led to the
qualification that the canals through which the ‘animal
spirits’ percolated should be very tiny. Theory has fooled
the greatest observers, even Vesalius when, at least in the
first edition of his Fabrica (1543), he hesitated to contradict
Galen’s view on the passage of blood through the
interventricular septum of the heart: ‘we are driven to
wonder at the handywork of the Almighty by means of
which the blood sweats from the right into the left ventricle
through passages which escape human vision’. John Hunter
(1728–93), actually a great experimentalist (Moore 2005),
offered a theoretical counterargument against the thesis of
nerves being hollow tubes: ‘nothing material is conveyed
from the brain by the nerves, nor vice versa from the body
to the brain; for if that was exactly the case, it would not be
necessary for the nerves to be of the same materials with
the brain . . .’. Eventually the existence of canaliculi was
disproved experimentally, among others by Monro primus
Book Review
(1698–1767) in Edinburgh, confirming 17th century
observations such as microscopical sections of a bovine
optic nerve by Leeuwenhoek (1632–1723), and physiological studies with nerve–muscle preparations by Borelli
(1608–79) and Swammerdam (1637–80). Alternative explanations were wanting, but some came close. Hartley
(1705–57) postulated ‘particular vibrations’ in nerves as
well as in the white matter of the brain, probably inspired
by Newton’s physics but not in the sense that he assumed
an analogy with musical strings. Bonnet (1720–93),
eponymously remembered through the description of the
syndrome of visual hallucinations in his partially blind
maternal grandfather, chose the term ‘movements’ for a
similarly corpuscular view of signal propagation without
transportation, within and between ‘nerve fibres’—fibre
being more a theoretical construct than a microscopical
structure according to present connotations.
At the same time, much debate revolved around the
question of ‘irritability’, an older term revived by the Swiss
physician Haller (1708–77), who thereby evoked a controversy with philosophical and even religious undertones.
Irritability of muscle tissue was its capability of contracting
through pricking, stretching, applying acrid substances and
especially by ‘a torrent [current] of electrical matter’. Haller
concluded that muscle harboured an intrinsic force (vis
insita), independent from its nerves. This mechanical
perception of muscle as a decentralized energy store was
fiercely opposed by Robert Whytt (1714–66), a Scot who,
like Haller, had studied with Boerhaave in Leiden. Whytt
maintained, mainly through theoretical reasoning, that a
‘sentient principle’ transmitted by the brain, spinal cord
and nerves was necessary as well as sufficient to explain
muscular contraction. He also postulated the existence of a
primary, immaterial principle governing motions and
actions, but did not go so far as the animist position that
the soul resides in every part and organ of the body. The
present-day author of one of the two chapters on the issue
considers the contest a tie; indeed Haller never attributed
true autonomy to muscle.
Electricity, a phenomenon (re)discovered by Cardano
(1501–76) and christened by Gilbert (1544–1603), emerged
as the solution to the riddle of nervous transmission towards
the end of the 18th century. An early line of research was the
study of electrical fish. Despite long-standing interest in the
shocks transmitted by these animals it was still undecided
whether they were mechanical or electrical in nature. In 1772,
John Walsh (1726–95), a wealthy gentleman with an interest
in natural history and a typical exponent of the
Enlightenment, journeyed to La Rochelle to study torpedoes.
On his return, Walsh struck up a collaboration with Hunter
and Cavendish (1731–1810), by which the existence of animal
electricity was confirmed beyond doubt—they even managed
to store it in Leiden jars. The discovery of electricity in
‘ordinary’ nerves is traditionally situated in 1786, when
Galvani (1737–98) hung some fresh frog legs on brass hooks
from the iron railings in his garden. His initial explanation
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was ‘fluidist’, in that he assumed secretion of an electrical
substance by the brain, an antiquated notion that the
physicist Volta (1745–1827) lost no time in attacking. It is
from this starting point that electrophysiology took off in the
next century.
These are, in brief, the main developments that can be
extracted from the compilation of individual essays
gathered in Brain, Mind and Medicine. Other chapters
describe the first inklings of cerebral localization (Pourfour
du Petit, Bonnet, Swedenborg), evolving ideas about
apoplexy, crazes about electrical treatments, and, unavoidably, dualism versus materialism. Gaps and overlaps are
inevitable in multi-author books, but the index might have
been more helpful: words such as ‘science’ and ‘nerve’
receive hordes of citations, while one looks in vain for some
persons, even if repeatedly mentioned in the text (e.g. Pivati
and Ingenhousz). Some authors indulge in footnotes, while
others introduce secondary citations—almost anathema in
an historical treatise.
The two books differ not only in content but also in
execution. Smail single-handedly tells a complicated though
at the same time compelling story about evolution and the
brain in 202 pages, notes excluded. Despite excursions on
byroads and the ushering in of other authors, the reader
never gets lost. The 379 double columns of the multiauthor book on 18th century neuroscience provide a wealth
of information, but in the form of a Diderot-like compilation from which the reader has to reconstruct the main
story. What the two books have in common other than the
brain as subject matter is that the authors venture in
foreign territory. The historian Smail valiantly enters an
arena where evolutionary biologists were already engaged in
bitter feuds. The scores of authors contributing bits and
pieces of 18th century neuroscience are for the most part
not historians, but physicians, psychologists, basic scientists
or philosophers. Both books are laudable attempts to bridge
Lord (CP) Snow’s ‘two cultures’, humanities and science, a
task becoming increasingly demanding as fragmentation of
knowledge continues. Flak from specialists will not be
wanting, but often the soil is most fertile in border zones
between disciplines.
Jan van Gijn
University Medical Centre Utrecht, The Netherlands
Advance Access publication September 19, 2008
doi: 10.1093/brain/awn210
Clarke E, Dewhurst K. An Illustrated History of Brain Function - Imaging
the Brain from Antiquity to the Present. San Francisco: Norman; 1996.
Israel JI. Radical Enlightenment. Oxford: Oxford University Press; 2001.
Medawar PB. Does ethology throw any light on human behaviour? In:
Pluto’s Republic. Oxford: Oxford University Press; 1982. p. 191–202.
Moore W. The Knife Man: The Extraordinary Life and Times of John
Hunter, Father of Modern Surgery. London: Bantam Press; 2005.
Porter R. Flesh in the Age of Reason. London: Allen Lane; 2003.
Sömmerring ST. Über das Organ der Seele. Königsberg: Friedrich
Nicolovius; 1796.