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He Shot Down the Tiny Adult Theory

Tomorrow is the birthday of German surgeon and physiologist Kaspar Friedrich Wolff, born in 1733. Regarded as the founder of embryology, Wolff published in 1759 a revolutionary work called Theoria generationis, which challenged the prevailing theory that each organism develops from a homunculus--or tiny version of an adult--inside a seed or sperm. Wolff proposed that groups of cells, initially unspecialized, differentiated into various tissues, organs, and systems. The idea that plants and animals are composed of cells was still controversial, and Wolff's findings were shunned for more than 50 years. But he eventually did get a measure of recognition: The Wolffian body, an embryonic structure in animals that develops into the kidney, is named after him.

[Source: Roy Porter, Ed., The Biographical Dictionary of Scientists (Oxford University Press, ed. 2, 1994).]