Viktor Hamburger

A German-American embryologist whose experiments on chicken embryos, done with Rita Levi-Montalcini, led to the discovery of nerve growth factor — the first protein shown to guide the growth of nerve cells, work that later won Levi-Montalcini a Nobel Prize. With Howard Hamilton he also published the Hamburger-Hamilton staging system in 1951, a standardized description of chick embryo development still used by developmental biologists today. He was regarded as one of the most influential neuroembryologists of the twentieth century.