Hermann was born in Berlin. In addition to his work in phonetics, he was influential as a physiologist. He opposed the notion, propounded by Emil du Bois-Reymond, that muscles contained an ordered series of "electromotive molecules" in favor of a theory of chemical activity. Hermann showed that the entire surface of an uninjured muscle was electrically equipotential. His discoveries in this field were instrumental to the modern use of the electrocardiograph as a diagnostic tool. He also was the first to explain the digestive process as being a decomposition of protein through acid hydrolysis to obtain the raw materials needed by cells.