Guarana , a paste formed chiefly from seeds of Paullinia sorbilis, and perhaps P. cupana, climbing shrubs of the order sapindaccce, growing in Brazil and on the banks of the Orinoco. The paste is dried into rough, hard, reddish brown masses, which may be reduced to powder. It is habitually used by the Brazilian Indians as a part of their diet, either mixed with other articles or as a drink. It is said to contain more than 5 per cent. of a crystallizable principle identical with caffeine, and has in addition tannic acid and two or three volatile oils. It has long been used in Brazil as a medicine, especially in the treatment of diseases of the bowels; but although known in Europe for a number of years, it has only recently received much attention. Its action upon the system in a state of health is apparently negative, as it affects neither pulse nor temperature. An increased capacity for mental labor, moderate wakefulness, and an influence upon the nervous system, similar to that produced by tea and coffee, have been observed. It evidently acts somewhat like a tonic; but more accurate observations than any we now possess are requisite in order to determine its physiological action upon the system.

It has recently been used both in this country and Europe with advantage in the treatment of headaches, especially those of a nervous character. It renders the greatest service in such cases when it is administered near the commencement of an attack, and repeated at short intervals. It is best given in milk, and should be repeated if necessary at intervals of half an hour, three or four times, in doses of from ten grains to half a drachm. In other nervous affections it has been tried, especially in nervous derangement of the stomach, but in these it has not been found useful. Its action closely resembles that of tea and coffee. A fluid extract has also been made. Its administration is contra-indicated by an inflammatory condition of the system.