Members of the lab shared ideas and techniques, and Spemann let the students work on their own projects, largely following their own interests (See cartoon of Spemann lab by Holtfreter, from Hamburger, 1988). Most of their time they spent in the lab, making observations on a number of different organisms using a variety of techniques. Otto Mangold, Hilde Proescholdt (who married Mangold), and Johannes Holtfreter all became important parts of Hamburger’s life, and Holtfreter remained a life-long friend whose creativity Hamburger greatly admired. Unfortunately, Hilde Mangold died in an explosion of a kerosene stove in her kitchen shortly after helping to carry out the research that led to the idea of the organizer and earned Spemann a Nobel Prize in 1935.
While others explored the effects of transplanting pieces of the embryo from one place to another or one embryo to another, Spemann suggested that Hamburger take up a very different topic: examining whether limb development required innervation from the central nervous system and the more general relationship between nerves and their peripheral target tissues. This proved a tremendously productive line of research that led Hamburger initially to postulate the existence of an inductive factor in the limb buds that stimulated nerve growth toward those limbs (what later became, in modified form, the identification of nerve growth factor (NGF, see below).
Hamburger completed his PhD in 1925 and left Freiburg to join Otto Mangold’s group at the Kaiser Wilhelm Institute for Biology outside of Berlin, but he returned in 1927 when Spemann hired him as a privatdozent to teach the “Grosse Prakticum” and further his research on embryonic induction. Most of his research involved transplanting pieces of salamander embryos to determine the effects on limb development.
Allen, Garland, Dletrich, Michael, Huber, Florian. 2016. "Victor Hamburger and Experimental Embryology." MBL History Project digital exhibit. http://history.archives.mbl.edu/exploring/exhibits/viktor-hamburger-and-experimental-embryology