Richard Burian, Jean Gayon: Genetics and medical research in France: the case of Boris Ephrussi (1901-1979). In contrast with other pioneers of the French school of molecular genetics (such as André Lwoff or Jacques Monod at the Pasteur Institute), Ephrussi did not work in a medical context. Trained as a classical zoologist at the Sorbonne, he devoted most of his scientific work to the comprehension of the genetic control of cellular differentiation, being exceptionnally skiful in breaking fronteers between experimental biological disciplines. But he never accepted to inflect his research in the direction of medical purposes, in spite of obvious links between some of the technical tools he used (tissue culture, cell hybridization) and majo...