Three pioneer physiologists, who found how do our bodies work

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We often wonder how human and animal bodies work ? Our bodies are an incredible assembly of countless systems. These systems make us see, run, hear, feel, move, talk, taste, react, think, interact, memorise and conceptualise. Further, these increasingly complex actions, are mostly harmonious, like a lifelong orchestra. Physiology is a branch of biology, that helps us understand, how does this orchestra function. Way back in 1959, Buenos Aires capital city of Argentina hosted 21st congress of International Union of Physiological Sciences. A postage stamp-set on this occasion, featured three physiologists who gave us some useful insights.

William Harvey (1578-1657): How does blood flow

William Harvey was an English physician. In 1628, he published a landmark book “Exercitatio Anatomica de Motu Cordis et Sanguinis in Animalibus“. This work describes how blood circulates in our body. Harvey pioneered his work, by performing some experiments in live animals. He identified right and left chambers in a beating heart. When limb veins were blocked or tied, heart world empty. This meant that veins take the blood to the heart. On the contrary, when arteries were tied, heart swelled up. This meant that arteries carry blood away from the heart. He confirmed this flow in human beings as well, and proved that flow of blood is unidirectional.

Harvey further contemplated that blood from arteries bathes muscles and tissues, and somehow it was all collected back to the veins. This work is incredible, as all these discoveries were done without a microscope. Harvey was not aware of capillaries, tiny channels that connect arteries and veins. None-the-less, this 88 page book in Latin, is available as a digital book here. Moreover, philatelists would love to find a 1957 William Harvey postage stamp, pasted on the inside cover of this digitalised book !!

While Harvey gave us the concept of circulatory system, its acceptance took a while. For centuries, scientists believed the view that arteries pumped air to the organs, and veins carried blood from liver to the heart. This view was more of a theory, proved wrong, by a series of experiments.

Claude Bernard (1813-1878): How do we digest food

Claude Bernard was a French Physician and a physiologist. An ardent supporter of experiments, he discovered three important functions in our body. First, he helped us understand process of digestion. He proved that juices from the pancreas, have a major role in digestion of food in our intestines. Second, he showed that liver not only consumes glucose, but also produces it. Third, stimulation of certain nerves can constrict or dilate blood vessels.

Claude Bernard also gave us a concept of milleu internal. This means that in order to function, our body maintains an internal environment. This internal environment means that various elements such as blood oxygen, carbon-dioxide, glucose, salt-concentration, temperature etc are normally within a narrow normal range. When this balance is disturbed, our systems do-not function as well. Today, for most part, our medical therapies try to restore this balance. As per Bernard “The constancy of the internal environment is the condition for free and independent life“. In 1865 Claude Bernard put forth a discourse on scientific thought, which is groundbreaking.

Ivan Pavlov (1849-1936): Conditioning reflexes

Pavlov studied medicine in Russia. In 1901, he developed the concept of reflex actions. This concept means that living beings can learn to perform complex actions as a reflex-task. Pavlov’s experiments involved dogs, who salivate when food was served. However, when dogs learned that another stimulus (such as a buzzer, bell, electric shock etc) will accompany food, they had a salivation reflex. This meant, that dogs salivated with buzzer, even in absence of food. Such experiments helped us understand process of neural learning. Our nerves, pass on a message to our brain. When this is repeated again and again, it becomes a reflex.

Pavlov won 1904 Nobel. In 1917 Russia became Soviet Union, and in 1921, Lenin issued a special Government decree to recognise Pavlov’s work. The influence of Pavlov on scientific society of the day was tremendous. In fact, Leningrad hosted 15th International Physiological Congress in 1935. Pavlov died of pneumonia the next year. It is said that even in his last moments, Pavlov asked one of his students to sit beside his bed and to record the circumstances of his dying. Probably, he wanted to create unique evidence of subjective experiences of this terminal phase of life.