Sympathin: Visceral Hormone

A Harvard professor opened up a cat and beheld certain belly muscles tickling its heart. That was of such profound physiological import that the professor, Walter Bradford Cannon, a great physiologist, last week took train to Yale, which once gave him an honorary Doctor of Science degree, to tell the Yale Medical Society just what he had done, what he had seen, what it all meant.

Professor Cannon had been searching for that thing in the body which stimulates the heart.

After he had made his cat comfortable on its back and insensitive to pain, he carefully slit open its torso to expose the viscera. Next he carefully cut practically every sympathetic nerve in the cat's body. Particularly, he cut the nerves running to the heart and every organ known to produce a hormone -- the thyroids, parathyroids, thymus, duodenum, liver, pancreas, adrenals, pineal gland, pituitary body, chorioid plexus and sexual organs.

These organs all belong to the vegetative or autonomic (sympathetic plus parasympathetic) nervous system which, so far as life itself goes, is more important than the central nervous system (brain and spinal cord). The central system controls the body's skeletal movements. When a person throws out his arms as he is about to fall, his brain is working. The muscles involved are striped muscles. (A steak is a slice of striped muscle.) When his stomach churns, smooth muscle is working. (Sausage casing is smooth muscle.) The heart is peculiar in this respect. Its muscle is half way between the striped and smooth kinds. It is connected by the vegetative nervous system with only smooth-muscled organs. These all function automatically. The will, that is the brain, cannot boss them. (However, some intense individuals learn how to control their own heart beats by hard thought.) Not only do these particular organs work automatically, they work together. They help each other out through their own nervous switchboard and through the blood stream which carries their messengers (hormones) around. Thus, the adrenal glands above the kidneys manufacture the hormone adrenalin, and adrenalin affects the heart.

Professor Cannon opined that other heart stimulants like adrenalin must also develop in other parts of the vegetative system. Hence his elegant operation on the cat.

After he had severed all the autonomic nerves which might obscure his research, he shook the cat's forepaws. Nothing happened. He shook its head. Nothing happened. He shook the hind quarters. At that the heart, whose nerves had been disconnected, started beating faster. He pinched the veins and arteries connecting the heart and the abdominal viscera he was watching. That is, with nerve or telegraph system cut off, he now dammed the blood stream through which a possible hormone might float. The cat's heart now returned to normal. Professor Cannon, wriggling the cat's hind part, released the pinched veins and arteries. The heart again beat faster than normal. Obviously the movements of the cat's lower muscles manufactured something which caused the faster beating: that is, a hormone similar in effect to adrenalin. Professor Cannon named his new hormone sympathin.

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