A glucoside derived from the root of the apple, pear, cherry, etc. Produces renal glycosuria and polyuria. The drug destroys the malarial parasites, but it is not safe to use in this connection. Its real use is in functional kidney tests. Dissolve 1-12 grain in 15 minims of a 0.5 per cent solution of sodium carbonate, and inject hypodermically. Glucose, if the permeability of the kidney is normal, should appear in the urine in from fifteen minutes to one-half hour and the secretion of sugar should continue for from two to four hours.

Phenolsulphonephthalein is also used in the functional test of the kidney. See "New and Nonofficial Remedies."