The author takes up the causation and prevention of deafness as well as its treatment. He lays considerable stress on the effect of adenoids or other conditions in the nasopharynx. After a summary of the usual methods of therapy employed by most otologists, he discusses in detail the theory of reeducation of the deaf by means of various sounds, from the time of Itard, in 1802, to the use of the apparatus mentioned in the title. Victor Urbantschitsch is the one who devised the elaborate system for the reeducation of the deaf by means of the voice. However, it is well known that this is of value in only a limited number of cases. The author states that with the electrophonoide the various tones of the human voice are reproduced, and, by conducting these to the ear, improvement in hearing is obtained in many cases. The apparatus is rather complicated.