"Not only must the truth be told, but also the cause of the error."—Aristoteles.1 The state of our knowledge concerning the response of warts to treatment is well described by Sir Norman Walker's remark, that : ". . . the ways of warts are mysterious, and they sometimes disappear in a few days under methods of treatment at which in the days of one's youth one was inclined to scoff." Sir Norman refers to the observation, that: "Crops of warts will sometimes vanish under the apparent influence of minute doses of arsenic . . ., Epsom salts . . ., or green iodide of mercury . . ., and the disappearance of large crops has been noted to follow the injection of salvarsan." But Sir Norman's remarks apply with, at least, equal force to the methods of treatment for warts by suggestion and irradiation, and more especially to the unorthodox mode of therapy by so-called magic, each of which is