Bohn's approach was mechanistic in that he grave predominately physical interpretations of vital processes. He experimented on the decapitated frog, declaring the reflex phenomena to be entirely material and mechanical, the general view of the time being that “vital spirits” were present in the nerve-fluid. Bohn showed that the nerves do not contain a “nerve juice”. (See p. 460 of the book.) Bohn also described the function of the heart in iatromechanical terms.