Johann Friedrich Meckel the Younger (1781-1833)

On the occasion of the 200th anniversary of the birthday of Johann Friedrich Meckel the Younger (1781-1833) it is appropriate to examine his contributions to the field of clinical genetics. Special emphasis is given to his laws of "diversity" and "reduction." These deal respectively with the evolutionary and developmental differences between organisms and the reasons for similarities in development of parts of an organism and the parts of different organisms. Meckel is an important pioneer of modern clinical teratology because he did not restrict his studies to normal development, but rather concentrated on its aberrations in his reflections on the history of development.