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WORKS
Before propounding his theories, William Harvey made it clear that
his intention was not to deprive his predecessors of their honor;
his sole intention was to use nature and to bring out the truth.
The Heart
The working of the heart was a puzzle to most of the anatomists
in the earlier centuries. As time passed a clear picture started
to evolve. The earlier prevailing notion was that blood moved in
the body because of arterial contractions. Harvey was able to discredit
this fact by his tireless dissections. He succeeded to establish
the relation between heart and blood circulation by dissecting the
heart and blood circulation systems of animals. According to Harvey
“I have used all my endeavor, bestowed all my pains on an attempt
to produce something that should be agreeable to the good, profitable
to the famed and useful to letters.”
Until the 17th century, the works of scientists like Claudis Galen was used in medical schools. By then Andrews Vesalius, a scientist, had proved many of Galen’s ideas wrong. Harvey was an admirer of Galen. His first law of contention on Galen’s theory was about the beating of the heart. According to Galen the beating of pulse was the same as that of respiration. Harvey was able to prove that when the heart was erected it rose upwards to a point and at this juncture it beats against the chest and due to this the pulse is felt. Even a common man could surmise from the way Harvey put forward his theories. A person in anger, or exhausted by running, or having a warm bath could feel the pulse beat rapidly, whereas the respiration was less compared to the heartbeat. This made it clear that heartbeat and respiration did not complement each other, they had entirely different origins.
The general ideas prevailed that the blood oozed through septum (the walls of the heart) from the right to the left ventricle. Harvey did away with this false conception. He made it clear that the septum of the heart was very thick compared to any part of the body. Nature has designed a more convenient passage: the pulmonary vein. The theory surrounding the septum sounded absurd as Harvey tried to prove that with aging the septum would become denser and would prevent the infiltration of blood. Harvey succeeded in laying bare these mysteries through his experiments. |
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He portrayed a vivid picture of working of the heart. The heart
works like a muscle, when it contracts the ventricles shrink and
blood is expelled out, this makes the color of the heart become
pale. When the heart rests the ventricle is filled with blood and
the crimson color returns; all these actions take place at the same
instant. The previous notion was that, the heart on its own had
the power of drawing blood into the ventricles. Caspar Bauhin and
John Roland, the famous anatomists, have observed that the heart
has four motions, which take place in four distinct times. Harvey
agrees with the four motions but not with the number of times. Harvey
points out that the two auricles move at the same time and the two
ventricles likewise, so the motion is performed in two times and
not in four.
Harvey’s observation about the heart is that all living creatures
possess one, the warm-blooded creatures have red blood and the smaller
creatures have pale blood. The heartbeats of the cold-blooded are
very slow, in winter these animals do not show any pulsation, they
‘live after the manner of vegetables’. Another amazing
thing that he noted was that a whole kingdom of 300 zoophytes exists
which have no heart, and the whole body works as a heart.
The heart is the source and fountain of all actions taking place
in the human body. Man’s whole life depends on the food he
eats; he can lead a normal life only if the digestion and distribution
of energy is perfect. It is the only organ, which contains blood
for general use; all other parts receive it to perform their particular
functions. The heart is situated in such an advantageous position
that it can distribute blood in due proportion, it can disburse
specified quantity, according to the size of the artery.
He studied the development of heart in chicks, within the first
week of incubation a drop of blood appears and it palpitates, then
the auricles develop and show constant signs of life. When the outline
of the body begins to take shape the ventricles appear, but they
are white and apparently bloodless with no signs of motion, so it
is believed that the auricles and ventricles come to life before
the heart and die after it. Harvey observed through his experiments
that the heart ceases to pulsate sooner than the auricles and then
the ventricle and finally all the other parts of the body come to
a rest or death occurs. Aristotle, the great philosopher sums it
up “Whence that in animals, which was last created, fails first
and that which was first, fails last.
By using greater diligence and investigation, and by frequent inspection
and numerous collating observations, he was able to reveal the truth,
he felt like ‘extricating himself from a labyrinth’. Harvey
learnt that when the heart becomes tense, the blood is expelled,
when it relaxes it receives the blood. Through his dissections,
he proved that when the chest of a living animal is laid open the
heart is seen alternatively moving and resting. When the right ventricle
contracts, the pulmonary artery is filled with blood and distended
by the blood forced into it, all the arteries are filled and they
pulsate due to this. The pulses of the arteries are due to the forceful
intake of the blood from the left ventricle.
Harvey was able to prove this beyond doubt when he treated a patient
with a large pulsating tumor on the right side of the neck, which
increased daily because of the blood received from the artery. The
connection between the heart and the artery was obvious only after
the postmortem of the patient. The pulse in the corresponding arm
was small because a large portion of blood was diverted to the tumor.
The conclusion was that whenever there is an impediment in the path
of the artery the arteries beat with less force.
Harvey was the first to adopt scientific methods for the solution
of biological problems; he was a forerunner of the method and even
today a true scientist follows Harvey’s approach. A 19th century
anatomist, William Osler praised Harvey for this mode of approach,
which marked the break of the modern spirit with the old traditions.
Careful observations and accurate description was not the end to
experiments, Osler said, “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.”
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