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Carroll Milton Williams (December 2, 1916 in Oregon Hill, Virginia October 11, 1991 in Watertown, Massachusetts) was an American zoologist known for his work in entomology and developmental biology—in particular, metamorphosis in insects, for which he won the George Ledlie Prize. He performed groundbreaking surgical experiments on and , and developed multiple new techniques, including the use of carbon dioxide as an anesthetic. His impact on entomology has been compared to that of Vincent Wigglesworth.
In 1942, he began a series of experiments on metamorphosis. In the most famous one, he cut a pupa in half and connected the two halves with a small tube, to study the effect of the lesions on the metamorphosis.
Next he studied the endocrine control of the development of the giant American silkworm Hyalophora cecropia, introducing carbon dioxide as a surgical anesthetic. He showed that a hormone from the brain activated the prothoracic glands to release the moulting hormone ecdysone. When the juvenile hormone is present also, larvae moult to another larval stage. Juvenile hormone is not present during the larval-to-pupal or the pupal-to-adult moults. The pupae enter diapause which is broken when the brain has been chilled for weeks, after which it releases the brain hormone. Williams was the first to isolate juvenile hormone and ecdysone. With his students he studied cocoon-spinning behavior and the profound metabolic shutdown during diapause, and was the first to discover and isolate cocoonase and cytochrome b5, as well as the "paper factor". He subsequently proposed that hormonal analogues could be used as by disrupting the developmental cycles of insects.
Williams was the chairman of the biology department at Harvard University from 1959 to 1962, and the Benjamin Bussey Professor of Biology from 1966 until his retirement in 1987. He was a fellow of the American Academy of Arts and Sciences, and was elected to the National Academy of Sciences, where he was a member of the Academy's council for two terms and chairman of biological sciences for one. He was also a member of the Institute of Medicine, the Pontifical Academy of Sciences, and the American Philosophical Society.
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