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Retrospect

Chemical messengers

At the beginning of the 20th century, the Russian physiologist Ivan Petrovich Pavlov was a star of world medicine, a pioneer in the important areas of the physiology of the heart, the nervous system and the digestive system. He had enormous influence on the development of behavioral theories and psychology, by carrying out his famous experiments with dogs and showing their conditioned and unconditioned reflexes. With a curriculum like this, there were few believers when English doctors Ernest Henry Starling and William Maddock Bayliss cogitated an explanation of the hitherto little known hormonal functions.

After all, Pavlov already had the answer: he believed that these functions were nervous reflexes. In 1902, a hundred years ago, Starling and Bayliss published the first article on a substance baptized secretin, taken from the pancreas. When injected into dogs, it would stimulate the organism to produce fluid. The Englishmen, then, drew up the concept of “chemical messengers”. That is, it is not nervous reflexes that activate secretion, but a few chemical substances that carry instructions to the cells, in animals and plants.

In 1905, Starling started to use the term “hormone”, from the Greek “to put in motion”. Today, over a hundred hormones are known, regulating development, the functions of several organs, and assist in reproduction and metabolism. On getting to know the Englishmen’s work, Pavlov admitted his error coolly. “Naturally, they are right”, he stated. “I do not have a patent on the discovery of truth.”

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