The "Yale Embryo," circa 1934

In 1934 Elizabeth Ramsey a recent Yale graduate was performing an autopsy on a young woman at New Haven Hospital when she discovered a tiny blob that would help define her career. The blob, an apparently healthy 14-day-old human embryo was arguably the youngest discovered to date. Ramsey donated it to the Carnegie Institution of Washington Department of Embryology in Baltimore (story pg. 48). Carnegie number 6734 became a fixture in the department's extensive collection of human embryos that would inevitably be used to develop the now standard "Carnegie Stages," the 23 developmental stages of embryonic growth based largely on the appearance of differentiated structures rather than on size or age.


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