Secret of Growth

One of science's deepest mysteries is what makes living creatures grow and what makes most of them stop growing as they reach maturity. In Nature, Professor Carroll M. Williams of Harvard describes research that may cast light on this basic mystery. He has extracted from mammalian tissues a "golden oil" that, injected into a caterpillar, stops its development and prevents its transformation into a butterfly.

Biologists guessed a generation ago that the metamorphosis of insects (changing from larvae to pupae and from pupae to adults) is probably controlled by a chemical hormone. Three years ago Dr. Williams extracted an oil from the...

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