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Article
March 12, 1932

LONDON

JAMA. 1932;98(11):899-901. doi:10.1001/jama.1932.02730370039022

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Abstract

The Descent of the Testis  Continuing his lectures at the Royal College of Surgeons, Sir Arthur Keith said that embryology had entered on a new era. Eighty years ago Owen taught that nature, in fashioning the animal body, worked to plan, much as a builder obeys an architect's specifications. Then came Darwin, who showed that every embryo was its own architect—that the powers which shaped the unfolding embryo were resident in its developing tissues. But while accepting Darwin's teaching, embryologists still tried to explain developmental events as the result of mechanical happenings — of foldings and bendings. Only recently had they escaped from this, when it was discovered that parts of a living embryo could be detached and maintained alive and that certain parts contained growth-controlling substances by which they can compel neighboring tissues to cooperate in producing a new and completed structure. Scarcely a surgical operation had not its

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