German founder of experimental pathology whose emphasis on the teaching of physiology and medical biochemistry helped give clinical medicine a scientific foundation.

Frerichs worked at the University of Breslau (1851–59) and then directed the Charité Hospital at the University of Berlin (1859–85). A leading exponent of clinical medicine supported by exacting laboratory analyses and experiments, he decisively influenced the development of his students, one of whom was Paul Ehrlich (Ehrlich, Paul), a corecipient of the 1908 Nobel Prize for Medicine for work in immunity. Frerichs' investigations into the general biochemistry of diseased organisms led to improvements in the diagnosis and treatment of diabetes and liver diseases.