Placebos ore pharmocologically inert substances, e. g. lactose, saline solution, starch. Their functions hove been listed as follows: a) to determine the physiological response to therapy b) to determine if the physiological response is changing and c) to check the validity of the experimental technique. In a study covering a wide variety of clinical problems, the incidence of placebo responses was reported to be approximately 35%. Placebos not only produce beneficial results but are also associated with toxic effects.