Often referred to as the founding father of developmental neurobiology, Viktor Hamburger is known for his work on the development of the nervous system in chick embryos and for defining and classifying the different stages in embryological development. He was elected to the National Academy of Sciences in 1953 for developing techniques of microneurosurgery; he was also honored for research which led to the discovery that developing nerve cells are dependent on the limbs to which they are connected. In 1989 he was awarded the National Medal of Science, and he is now the Edward Mallinckrodt Distinguished University Professor Emeritus of Biology at Washington University in St. Louis.
The first of three sons, Hamburger was born to Max and Else Hamburger in the small town of Landeshut, Silesia, which was then an eastern province of Germany, but is now part of Poland. As a child, Hamburger was fascinated by the plant and animal life around him and one of his earliest desires was to be a naturalist. At six years old, he collected assorted plants and fossils from quarries. At that time, he also had an aquarium in which he observed frog and salamander eggs develop into tadpoles and larvae and then metamorphose. Hamburger was educated at home by a private teacher until the age of nine, when he entered the gymnasium, graduating in 1918.
Hamburger studied zoology at several universities before settling on the University of Freiburg. He studied at the University of Breslau from 1918 to 1919, Heidelberg from 1919 to 1920, and then Munich from 1921 to 1922. It was here that Hamburger met Hans Spemann--a Nobel laureate and the leading German experimental embryologist. Spemann had discovered what he called the "organizer" in amphibian embryos: a portion of an embryo, when transplanted to another region in the embryo, grows an extra embryo around the transplanted piece; this piece of tissue has the organizing power to induce embryonic growth.
Under Spemann, Hamburger began experiments on the development of the nervous system in amphibian embryos, mostly in those of frogs and salamanders collected from local brooks and ponds. Spemann taught Hamburger to perform techniques for microsurgery which he had developed. Within two years of beginning work on the embryonic nervous system, Hamburger published a paper which refuted another scientist's earlier hypothesis, and earned him his doctorate in zoology in 1925. Hamburger continued his work in Freiburg, researching young nerve cells and the muscles they supply with nerves, until 1932, when he won a one-year Rockefeller Foundation fellowship. He left Germany for what he thought would be only a year and traveled to the University of Chicago to work with avian embryologist Frank Rattray Lillie. Hamburger brought to Chicago his exacting technique of microsurgery, modified for chick embryos. Until this time amphibians had been the worldwide standard object of study for embryology in laboratories; Hamburger's work in Chicago created new avenues for examining the embryos of complex organisms closer to those of mammals. His work with chick transplantations revealed that the limbs of chick embryos grow even after being transplanted.
Hamburger, who is Jewish, expected to return to Germany in 1933, but he was notified by German colleagues that he should not return because of the political climate. He stayed at the University of Chicago as an instructor for two more years before accepting an appointment as an assistant professor of zoology at Washington University. By 1941, he was appointed professor and chairman of that department, a position he would retain until 1966.
At Washington University, Hamburger continued his work on embryos, and with H. L. Hamilton he described and classified the stages of development of the chick embryo. Hamburger was particularly interested in the relationship between the limbs of an embryo and its nervous system. Just after World War II, he read an article on this subject by the Italian neurobiologist Rita Levi-Montalcini; she had repeated an experiment he had done and was disputing his conclusions. "It turned out Rita was right as usual," Hamburger is quoted as saying in the Washington University Magazine. Hamurger invited her to work with him in St. Louis.
Once they began working together, Hamburger and Levi--Montalcini found that when the embryonic limb was removed, the motor nerve cells that were to supply the limb with nerves failed to develop. The growth of the nerve cells was dependent on messages from the limb, also called the target. The questions the two scientists now faced were how and why these two components were interdependent. Hamburger theorized that there was some kind of communication between the limb and the spinal cord which triggered the production of motor neurons, but his conclusions were based on the principles of embryonic organization which he had learned in Spemann's laboratory. However, by painstakingly counting cells, Levi--Montalcini found that the development of nerve cells proceeded normally for a short time after the limb was removed. They were generated even without the limb, but they could not stay alive without instructions from it. The limb was somehow responsible for maintaining the life of the nerve cells. Levimdash;Montalcini identified a chemical substance produced in the peripheral target, called nerve growth factor (NGF), which sustained the nerve cells. For this discovery, she was awarded the Nobel Prize with biochemist Stanley Cohen in 1986, despite the fact that Hamburger did most of the writing of joint papers in 1951 and 1953 and "had considerable conceptual input," as Hamburger said in a letter to Arnold.
As the work done by Levi-Montalcini and Cohen revealed more of the extraordinary properties of NGF, Hamburger withdrew from the project, feeling that he could not contribute more since the work had moved into the biochemical realm. In the late 1950s, Hamburger's research turned toward embryonic behavior. Psychologists had been arguing for some time about the source of behavior, some contending that it is learned, others that it is inherited. Hamburger made a little window in an egg--"like a window display in a department store," he told the Washington University Magazine--and he observed every movement of the embryos. He found that their movement was "generated autonomously in the nervous system" and was independent of outside stimuli, dispelling the notion set forth by behaviorists like B. F. Skinner. This study placed Hamburger in the center of disputes with the psychologists whose research he had called into question.
Hamburger has been described as one of the "supreme biologists of our time," and Stanley Cohen has said of him in the Washington University Magazine: "I learned from Viktor how an embryologist thinks. He is the epitome of a classical embryologist." Hamburger sees himself as one of a dying breed, however, with experimental embryology being effectively replaced by molecular biology. He retired in 1983 and has written a book on Hans Spemann, which is what he calls "the only authentic history of this scientific era which is now closed."
Hamburger married Martha Fricke in 1927, with whom he had with two daughters. An unpretentious man, Hamburger loves art, a trait he acquired from his father. Cohen considers him "a member of a vanishing breed who are not only scientists but have very broad cultural interests and a world view. Whether it is in history or art, Viktor is an extraordinarily well-rounded person and most kind." In October of 2000, scientists from around the United States gathered at Washington University to celebrate Hamburger's centennial birthday.
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