In South America particularly in the Gran Chaco region, two species of plants of incalculable therapeutic value when properly applied, exist. These are known as Caapi or ayahuasca (Banisteria caapi Spruce) and Hataj, which is also called cebil, cohoba, vilca and curupa. Both plants have almost identical properties, serving as stimulants in small doses and as anaesthetics in larger quantities, also stimulating visions in the latter case. Their use dates from ancient times among all Indians of South America who made use of their magic properties on the occasion of their ritual and religious ceremonies. Caapi was imbibed in liquid form, a decoction from its leaves and bark; hataj was inhaled as a dust from seeds toasted previously. Special nasal tubes were used for inhaling. The state of euphoria and sopor which followed was accompanied by visions of every kind attributed to magie influences. This state permitted them to feel a presentiment of events, cure illness and speak to the Greater Spirits of the tribe. Consequently, whenever the tribe met difficult problems, they were resolved by consulting the Cemi or Greater Spirits through a special ceremony or meeting of witches where it was indispensable to put oneself in a trance through the medium of this drug. The potency of both drugs suggest the possibilities of their application in modem medicine as stimulants and anaesthetics. This would not be the first time that the empirical medicine of the aborigines has given materials of inestimable value to modem medicine, to be made available to civilization.