First description and definition of electrotonus.

A pupil of J. Müller, Emil du Bois-Reymond was the founder of modern electrophysiology. He introduced faradic stimulation and made an exhaustive investigation of physiological tetanus. Above is a collective edition of his writings on the subject. Extracts were translated into English in H.B. Jones, On animal electricity … London, 1852, and more extensive portions in C.E. Morgan, Electrophysiology and therapeutics, New York, 1868. Digital facsimile from the Internet Archive at this link.