Introduction; experimental studies; psychogalvanic studies of pain and fear; apparatus; observers; preliminary adjustment and instructions; affective situations; treatment of the psychogalvanic results; the relation of the breathing changes to the psychogalvanic reflex; introspections of fear; comparison between introspective and psychogalvanic results; conclusions; bibliography. * Professor J. N. Pearce, of the department of physical chemistry, very kindly designed the electrodes.