In Primitive Psycho-Therapy and Quackery, the writer has sought to emphasize the fact that the efficiency of many primitive therapeutic methods, and the success of charlatanry, are to be attributed to mental influence. The use of spells and incantations, the practice of laying-on of hands, the cult of relics, mesmerism, and metallo-therapy, have been important factors in the evolution of modern mental healing. The method of their operation, a mystery for ages, is revealed by the word suggestion.