William
HarveyWilliam Harvey (April 1, 1578 - June 3, 1657) was a medical doctor
who first correctly described in exact detail the circulatory system
of blood being pumped around the body by the heart. This developed the
ideas of René Descartes who in his Description of the Human Body
said that the arteries and veins were pipes and carried nourishment
round the body. Many believe he discovered and extended early Muslim
medicine especially the work of Ibn Nafis, who had laid out the principles
and major arteries and veins in the 13th century.
Early life and education
Born in Folkestone, England, Harvey was educated at the King's School,
Canterbury, at Gonville and Caius College, Cambridge, from which he
received a BA in 1597, and at the University of Padua, where he studied
under Fabricius, graduating in 1602. He returned to England and married
Elizabeth Brown, daughter of the court physician to Elizabeth I.
He became a doctor
at St. Bartholomew's hospital in London (1609-43) and a Fellow of the
Royal College of Physicians.
New circulatory
model
He announced his discovery of the circulatory system in 1616 and in
1628 published his work Exercitatio Anatomica de Motu Cordis et Sanguinis
in Animalibus (An Anatomical Exercise on the Motion of the Heart and
Blood in Animals), where, based on scientific methodology, he argued
for the idea that blood was pumped around the body by the heart before
returning to the heart and being recirculated in a closed system.
This clashed with
the accepted model going back to Galen, which identified venous (dark
red) and arterial (brighter and thinner) blood, each with distinct and
separate functions. Venous blood was thought to originate in the liver
and arterial blood in the heart; the blood flowed from those organs
to all parts of the body where it was consumed. It was for exactly these
reasons that the work of the "heathen" Ibn Nafis had been
ignored.
Embryology
Harvey also conducted research in embryology in his later career, writing
On the Generation of Animals (De Generatione) in 1651. He supported
the Aristotelian theory that embryos formed gradually and did not possess
the characteristics of an adult in early stages. He also hypothesized
the existence of a mammalian egg, and dissected dozens of deer in the
King's hunting park in hopes of finding one, although he failed to do
so.
Criticism of Harvey's
Work
Harvey's ideas were
eventually accepted during his life-time. His work was attacked, notably
by Jean Riolan in Opuscula anatomica (1649) which forced Harvey to defend
himself in Exercitatio anatomica de circulatione sanguinis (also 1649)
where he argued that Riolan's position was contrary to all observational
evidence. Harvey was still regarded as an excellent doctor, he was personal
physician to James I (1618-25) and Charles I (1625-47) and the Lumleian
lecturer to the Royal College of Physicians (1615-56). Marcello Malpighi
later proved that Harvey's ideas on anatomical structure were correct;
Harvey had been unable to distinguish the capillary network and so could
only theorize on how the transfer of blood from artery to vein occurred.
Even so, Harvey's
work had little effect on general medical practice at the time —
blood letting, an idea based on the incorrect theories of Galen, continued
to be a popular practice (and continued to be so even after Harvey's
ideas were accepted). Harvey's work did much to encourage others to
investigate the questions raised by his research, and to revive the
Muslim tradition of scientific medicine expressed by Nafis, Ibn Sina
and of course Rhazes.
William Harvey
(1578-1657)
Galen, a Asiatic-Greek physician who lived between the years 130 and
201 is described as having been a voluminous writer on medical and philosophical
subjects.1 Galen is to medicine what Ptolemy2 was to astronomy. He gathered
up all the medical knowledge that was known to his time. (Galen was
a careful dissector and was the first to diagnose by the pulse.) The
facts compiled by Galen amounted to a slim volume indeed, but it was
all that mankind had until William Harvey came along, some 1300 years
later. Galen had at least concluded the cardiovascular system carried
blood and not air, and also managed to cast some doubt on the theories
of Aristotle who thought that maybe blood arose in the liver; and the
thoughts of others, that the pounding in a person's chest was but the
soul speaking to us.
Harvey lived during the Elizabethan period of England.3 He had the good
fortune, upon returning from Italy where he had completed his medical
education, to marry the daughter of Elizabeth's physician. This connection
meant that Harvey did not have to work too hard at making a living,
thus leaving time for him to pursue medical research. By 1616 he was
lecturing before the College of Physicians on the circulation of the
blood. His notes (yes! he had extremely bad hand writing) built up into
a considerable mass, as he went about, through the years, cutting up
animals and giving lectures on his findings.4 Harvey may have realized
right along the importance of getting his work in print, but he was
in no hurry; like Copernicus, Harvey must have thought that his work
was never quite good enough, but, nonetheless, it was plainly an advance
on the accepted theories of Galen. His theories, to use own words:
"[It] is of so novel and unheard-of character, that I not only
fear injury to myself from the envy of a few, but I tremble lest I have
mankind at large for my enemies, so much does wont and custom, that
has become as another nature, and doctrine once sown and that has struck
deep root and rested from antiquity, influence all men."
And, Harvey recognized the problem with "journalism" as it
existed then, and, as it continues to exist today:
"The crowd of foolish scribblers is scarcely less than the swarms
of flies in the height of summer, and threatens with their crude and
flimsy productions to stifle us as with smoke."
Harvey, at the age of 50, in 1628, came quietly to the world stage when
he saw to the publication in Germany of a 72 page volume of his work
(written in Latin as were all learned articles of the day). It was at
the Frankfurt book fair that there stood a stack of newly printed books
with the title, Exercitatio Anatomica de Motu Cordis et Sanguinis in
Animalibus (Anatomical Exercise on the Motion of the Heart and Blood
in Animals), or, as it came to be known, De Motu Cordis. The earlier
theories were refuted and Harvey's theory was advanced and has held
firm ever since. (The only thing Harvey could never figure out, though
he recognized it took place, was how the blood was transferred over
from the arteries to the veins. The riddle was solved a few years after
Harvey's death when a professor at Bologna (Italy), Marcello Malpighi,
saw, through the newly-invented microscope, an instrument not available
to Harvey, the capillary network.)
As the fame of De Motu Cordis spread, the critics came at Harvey from
all directions. "'Twas believed by the vulgar that he was crack-brained,
and all the physicians were against him." For the most part Harvey
ignored his critics, though it should be noted that his medical practice
suffered. But, finally, 21 years after the initial publication of De
Motu Cordis, in 1649, at age of 71 (he was to live to age 79), Harvey
came back with a small volume where, in it, he gave his detailed replies.
The major difference between Harvey and his predecessors, was -- methodology.
Harvey determined to start out, so to speak, with a blank fact book
and distinguished it from his theory book. Nothing would go down in
his fact book unless tested and would readily remove it if it did not
bear out on a re-test. Harvey went beyond mere superficial observation;
and, he took deliberate steps so as not to be hampered by superstition
or antiquated theories. Harvey was the first to adopt the scientific
method for the solution of biological problems. Every true scientist,
since, has followed Harvey's approach.
I shall end this short note on William Harvey by turning to William
Osler:
"... it [De Motu Cordis] marks the break of the modern spirit with
the old traditions. No longer were men to rest content with careful
observation and with accurate description; no longer were men to be
content with finely spun theories and dreams, which "serve as a
common subterfuge of ignorance"; but here for the first time a
great physiological problem was approached from the experimental side
by a man with a modern scientific mind, who could weigh evidence and
not go beyond it, and who had the sense to let the conclusions emerge
naturally but firmly from the observations." (Attributed to Sir
William Osler, 1849-1919.)
Harvey, William
(1578-1657)
English physician
who, by observing the action of the heart in small animals and fishes,
proved that heart receives and expels blood during each cycle. Experimentally,
he also found valves in the veins, and correctly identified them as
restricting the flow of blood in one direction. He developed the first
complete theory of the circulation of blood, believing that it was pushed
throughout the body by the heart's contractions. He published his observations
and interpretations in Exercitatio Anatomica de Motu Cordis et Sanguinis
in Animalibus (1628), often abbreviated De Motu Cordis.
Harvey also noted,
as earlier anatomists, that fetal circulation short circuits the lungs.
He demonstrated that this is because the lungs were collapsed and inactive.
Harvey could not explain, however, how blood passed from the arterial
to the venous system. The discovery of the connective capillaries would
have to await the development of the microscope and the work of Malpighi.
He was heavily influenced by the mechanical philosophy in his investigations
of the flow of blood through the body. In fact, he used a mechanical
analogy with hydraulics. He could not, however, explain why the heart
beats. Furthermore, Harvey used quantitative methods to measure the
capacity of the ventricles.
Harvey was the first
doctor to use quantitative and observation methods simultaneously in
his medical investigations. In Exercitationes de Generatione Animalium
(On the Generation of Animals, 1651), he was extremely skeptical of
spontaneous generation and proposed that all animals originally came
from an egg. His experiments with chick embryos were the first to suggest
the theory of epigenesis, which views organic development as the production
in a cumulative manner of increasingly complex structures from an initially
homogeneous material.