Dayap

Uses

The essence (essential oil) and juice of the fruit are the parts of the plant used in therapeutics. The essence extracted from the rind is yellow, fragrant, slightly bitter; density, 0.856; boiling point 165°. The juice which is turbid and pale yellow in color contains 9% citric acid, 3–5% gum and sugar and 2–8/10% inorganic salts. The essence is used to flavor certain pharmaceutical preparations, and is a diffusible stimulant which may be given internally in doses of 3–6 drops on a little sugar. The bitter rind is occasionally used in infusion as a stomachic and stimulant. The juice is most commonly used in lemonade, a cooling drink which, used intemperately in the Philippines, is apt to cause gastro-intestinal trouble, so commonly attributed to “irritation,” but really the result of a general atony of the digestive organs. Lemon juice is also used with very good results as a local cleansing application for sore throat, as well as externally on fetid ulcers. In some forms of malarial fever it seems to have given satisfactory results, administered internally.

In many navies lemon juice forms a part of the sea ration as a preventive of scurvy, upon which it exercises a real and noteworthy action. The Danish navy adopted it for this purpose in 1770, the English navy followed, then the French and possibly others. The English call it lime-juice, and its preventive dose is 30–40 grams a day. Its curative dose is 100–150 grams a day. To preserve the lime-juice it was bottled with a layer of oil, which, floating on the surface kept it from contact with the air; but this process gave it a bad taste as did also the addition of sulphate of calcium, and at present the English add, to each liter of juice, 60 grams of alcohol, which preserves it perfectly. Fonssagrives says that the antiscorbutic action of lemon juice is due rather to the vegetable juice itself than to the citric acid which it contains.

Botanical description

A most familiar tree 11° or more high, trunk with solitary thorns. Leaves ovate, obtuse, acute-toothed, the petiole bearing serrate wings. Calyx 4–6-toothed. Corolla, 4 thick petals. Filaments 10–25 on the receptacle, some joined and bearing 2–3 anthers. Fruit thin-skinned, globular, about 1′ in diameter; the rind adheres closely to the pulp.

(This fruit closely resembles, if it is not identical with the lime fruit, C. Limetta, or C. Bergamia, Risso, though Gray states that the leaf of the latter has a wingless petiole.—J. B. T.)