Several years ago, in an endeavor to study experimentally the emotional reactivity of various psychopathic personalities, an investigation was made of the psychogalvanic reflex. In attempts to standardize the records so that the responses would be strictly comparable, however, great individual variations were encountered in the resistance offered by the body to the passage of a constant galvanic current. In order that this suggestion might be followed further, therefore, the electrical resistance was measured in each person to whom the psychogalvanic association test was given. When it was found that these incidental readings of resistance seemed to vary to a greater degree with different types of mental illness than did the psychogalvanic response, a detailed investigation of the electrical resistance of the human body was undertaken1in the hope that the significance of the more basic phenomenon of the resistance variations might be determined. In preliminary records, the lowest