Claude Bernard (July 12, 1813 â€“ February 10, 1878) was a French physiologist. Historian of science I. Bernard Cohen of Harvard University called Bernard "one of the greatest of all men of science". Among many other accomplishments, he was one of the first to suggest the use of blind experiments to ensure the objectivity of scientific observations.
was born in 1813 in the village of Saint-Julien near Villefranche-sur-SaĂ´ne. He received his early education in the
Jesuit school of that town, and then
proceeded to the college at Lyon, which,
however, he soon left to become assistant in a druggist's
His leisure hours were devoted to the composition of a
comedy, and the success it
achieved moved him to attempt a prose drama in five acts,
Arthur de Bretagne
At the age
of twenty-one in 1834 he went to Paris, armed with
this play and an introduction to Saint-Marc Girardin, but the critic
dissuaded him from adopting literature as a profession, and urged
him rather to take up the study of medicine.
Bernard followed, and in due course he became interne
the Hotel Dieu
. In this way he was
brought into contact with the great physiologist, FranĂ§ois Magendie, who was physician
to the hospital, and whose official 'preparateur' at the CollĂ¨ge de
France he became in 1841.
Memorial plaque in Paris marking the
site of Claude Bernard's laboratory from 1847 until his death in
In 1845 Bernard married FranĂ§oise Marie (Fanny) Martin for
convenience; the marriage was arranged by a colleague and her dowry
helped finance his experiments. In 1847 he was appointed Magendie's
deputy-professor at the college, and in 1855 he succeeded him as
full professor. Some time previously Bernard had been chosen
the first occupant of the newly-instituted chair of physiology at
the Sorbonne. There no laboratory was provided for his use,
but Louis Napoleon, after an
interview with him in 1864, supplied the deficiency, at the same
time building a laboratory at the MusĂ©um
national d'Histoire naturelle in the Jardin des Plantes, and establishing a professorship, which Bernard
left the Sorbonne to accept in 1868, the year in which he was
admitted a member of the AcadĂ©mie
When he died he was accorded a public funeral â€“ an honor which had
never before been bestowed by France on a man of science.
interred in Le PĂ¨re Lachaise Cemetery in Paris.
Claude Bernard's aim, as he stated in his own words, was to
establish the use of the scientific
in medicine. He dismissed many previous misconceptions,
took nothing for granted, and relied on experimentation. Unlike his
contemporaries, he insisted that all living creatures were bound by
the same laws as inanimate matter.
Claude Bernard's first important work was on the functions of the
gland, the juice of which he
proved to be of great significance in the process of digestion;
this achievement won him the prize for experimental physiology from
the French Academy of
. A second investigation - perhaps his most famous -
was on the glycogenic function of the liver
in the course of this he was led to the conclusion, which throws
light on the causation of diabetes
, that the liver, in addition to secreting bile, is the
seat of an internal secretion, by which it prepares sugar at the
expense of the elements of the blood passing through it. A third
research resulted in the discovery of the vaso-motor system. While
engaged, about 1851, in examining the effects produced in the
temperature of various parts of the body by section of the nerve or
nerves belonging to them, he noticed that division of the cervical
sympathetic gave rise to more active circulation and more forcible
pulsation of the arteries in certain parts of the head, and a few
months afterwards he observed that electrical excitation of the
upper portion of the divided nerve had the contrary effect. In this
way he established the existence of vaso-motor nerves, both
vaso-dilator and vaso-constrictor.
is the key process
with which Bernard is associated. He wrote, "La fixitĂ© du milieu
intĂ©rieur est la condition d'une vie libre et indĂ©pendante"
("The constancy of the internal environment is the condition
for a free and independent life"
). This is still the
underlying principle of homeostasis today.
The study of the physiological action of poisons was also a
favourite one with him, his attention being devoted in particular
and carbon monoxide
Bernard practiced vivisection
disgust of his wife and his daughter. He firmly believed that the
advancement of medicine and the relief of human suffering justified
the suffering of animals but his wife was not convinced, the couple
were officially separated in 1869 and his wife went on to actively
campaign against the practice of vivisection*.
His wife and daughter were not the only ones disgusted by the
cruelty of Bernard's animal experiments. The physician-scientist
George Hoggan spent four months observing and working in Bernard's
laboratory and was one of the few contemporary authors to chronicle
what actually went on there. He was later moved to write that his
experiences in Bernard's lab had made him "prepared to see not only
science, but even mankind, perish rather than have recourse to such
means of saving it."
Introduction to the Study of Experimental Medicine
In his major discourse on scientific method, An Introduction to
the Study of Experimental Medicine
(1865), Claude Bernard
describes what makes a scientific theory good and what makes a
scientist important, a true discoverer. Unlike many scientific
writers of his time, Bernard writes about his own experiments and
thoughts, and uses the first person.
Known and Unknown
. What makes a scientist important, he
states, is how well he or she has penetrated into the unknown. In
areas of science where the facts are known to everyone, all
scientists are more or less equalâ€”we cannot know who is great. But
in the area of science that is still obscure and unknown the great
are recognized: â€śThey are marked by ideas which light up phenomena
hitherto obscure and carry science forwardâ€ť.
Authority vs. Observation
. It is through the experimental
method that science is carried forward--not through uncritically
accepting the authority of academic or scholastic sources. In the
experimental method, observable reality is our only authority.
Bernard writes with scientific fervor:
Induction and Deduction
- â€ťWhen we meet a fact which contradicts a prevailing theory, we
must accept the fact and abandon the theory, even when the theory
is supported by great names and generally acceptedâ€ť
. Experimental science is a
constant interchange between theory and fact, induction and
deduction. Induction, reasoning from the particular to the general,
and deduction, or reasoning from the general to the particular, are
never truly separate. A general theory and our theoretical
deductions from it must be tested with specific experiments
designed to confirm or deny their truth; while these particular
experiments may lead us to formulate new theories.
Cause and Effect
. The scientist tries to determine the
relation of cause and effect. This is true for all sciences: the
goal is to connect a â€śnatural phenomenonâ€ť with its â€śimmediate
cause.â€ť We formulate hypotheses elucidating, as we see it, the
relation of cause and effect for particular phenomena. We test the
hypotheses. And when an hypothesis is proved, it is a scientific
theory. â€śBefore that we have only groping and empiricismâ€ť
Verification and Disproof
. Bernard explains what makes a
theory good or bad scientifically:
- â€śTheories are only hypotheses, verified by more or less
numerous facts. Those verified by the most facts are the best, but
even then they are never final, never to be absolutely
When have we verified that we have found a cause? Bernard
- Indeed, proof that a given condition always precedes or
accompanies a phenomenon does not warrant concluding with certainty
that a given condition is the immediate cause of that phenomenon.
It must still be established that when this condition is removed,
the phenomen will no longer appearâ€¦.
We must always try to disprove our own theories. â€śWe can solidly
settle our ideas only by trying to destroy our own conclusions by
counter-experimentsâ€ť (p. 56). What is observably true is the only
authority. If through experiment, you contradict your own
conclusionsâ€”you must accept the contradiction--but only on one
condition: that the contradiction is PROVED.
Determinism and Averages
. In the study of disease, â€śthe
real and effective cause of a disease must be constant and
determined, that is, unique; anything else would be a denial of
science in medicine.â€ť In fact, a â€śvery frequent application of
mathematics to biology [is] the use of averagesâ€ťâ€”that is,
statisticsâ€”which may give only â€śapparent accuracy.â€ť Sometimes
averages do not give the kind of information needed to save lives.
- A great surgeon performs operations for stone by a single
method; later he makes a statistical summary of deaths and
recoveries, and he concludes from these statistics that the
mortality law for this operation is two out of five. Well, I say
that this ratio means literally nothing scientifically and gives us
no certainty in performing the next operation; for we do not know
whether the next case will be among the recoveries or the deaths.
What really should be done, instead of gathering facts empirically,
is to study them more accurately, each in its special
determinismâ€¦.to discover in them the cause of mortal accidents so
as to master the cause and avoid the accidents.
Although the application of mathematics to every aspect of science
is its ultimate goal, biology is still too complex and poorly
understood. Therefore, for now the goal of medical science should
be to discover all the new facts possible. Qualitative analysis
must always precede quantitative analysis.
Truth vs. Falsification
. The â€śphilosophic spirit,â€ť writes
Bernard, is always active in its desire for truth. It stimulates a
â€śkind of thirst for the unknownâ€ť which ennobles and enlivens
scienceâ€”where, as experimenters, we need â€śonly to stand face to
face with natureâ€ť The minds that are great â€śare never
self-satisfied, but still continue to striveâ€ť Among the great minds
he names Joseph Priestly
Meanwhile, there are those whose â€śminds are bound and crampedâ€ť They
oppose discovering the unknown (which â€śis generally an unforeseen
relation not included in theoryâ€ť) because they do not want to
discover anything that might disprove their own theories. Bernard
calls them â€śdespisers of their fellowsâ€ť and says â€śthe dominant idea
of these despisers of their fellows is to find othersâ€™ theories
faulty and try to contradict themâ€ť They are deceptive, for in their
experiments they report only results that make their theories seem
correct and suppress results that support their rivals. In this
way, they â€śfalsify science and the factsâ€ť:
Discovering vs. Despising
- They make poor observations, because they choose among the
results of their experiments only what suits their object,
neglecting whatever is unrelated to it and carefully setting aside
everything which might tend toward the idea they wish to
. The â€śdespisers of their
fellowsâ€ť lack the â€śardent desire for knowledgeâ€ť that the true
scientific spirit will always haveâ€”and so the progress of science
will never be stopped by them. Bernard writes:
- Ardent desire for knowledge, in fact, is the one motive
attracting and supporting investigators in their efforts; and just
this knowledge, really grasped and yet always flying before them,
becomes at once their sole torment and their sole happinessâ€¦.A man
of science rises ever, in seeking truth; and if he never finds it
in its wholeness, he discovers nevertheless very significant
fragments; and these fragments of universal truth are precisely
what constitutes science.
- See Cohen's Foreword to the Dover edition (1957) of Bernard's
classic on scientific method, An Introduction to the Study of
Experimental Medicine (originally published in 1865)
- All page references refer to the Dover edition of 1957. *
Bernard, Claude. An Introduction to the Study of Experimental
Medicine, 1865. First English translation by Henry Copley
Greene, published by Macmillan & Co., Ltd., 1927; reprinted in
- p. 42.
- p. 164).
- p. 74.
- p. 165.
- p. 55.
- P. 137.
- p. 221.
- p. 222.
- p. 37.
- p. 38.
- P. 38.
- P. 22.
- Holmes, Frederic Lawrence. Claude Bernard and Animal
Chemistry: The Emergence of a Scientist. Harvard University