Most cultures of man, from earliest times, have had recourse to some form of narcotic, often hallucinogenic, drug. These hallucinogens, often derived from plants, have frequently been used within a religious context. In recent years peyote, Indian hemp and lysergic acid derivatives have received much attention, but there are many other similar drugs used by local populations whose existence and use are still being investigated by ethnobotanists. In this respect, Professor R. E. Schultes (1915–2001) made extensive studies of such plants in South America and has emphasized the great need for recording the wealth of knowledge possessed by native tribes on narcotic plants before the activities of these peoples are overcome by ‘civilization’.
With the exception of cannabis, the principal known hallucinogenic plants contain alkaloids related to the neurophysiological transmitters noradrenaline and 5-hydroxytryptamine (serotonin).