Proliferation, differentiation and degeneration in the spinal ganglia of the chick embryo under normal and experimental conditions.

In this paper Viktor Hamburger [5] and Rita Levi-Montalcini [6] collaborated to examine the effects of limb transplantation [7] and explantation on neural development [8]. In 1947 Hamburger invited Levi-Montalcini to his lab at Washington University [9] in St. Louis to examine this question. Independently, each had previously arrived at opposing conclusions based on the same data. Hamburger concluded that limb transplantations caused the ganglia to develop more connections and grow larger while Levi-Montalcini concluded that the ganglia first produce a large amount of neurons, then degenerate the unsuccessful neurons. She concluded that larger ganglia must be due to the increase in successful connections. This joint paper, published in the Journal of Experimental Zoology [10] in 1949, corroborated the findings reported by Levi-Montalcini and established that nerve degeneration is an integral part of development.