This section is from the book "A Treatise On Therapeutics, And Pharmacology Or Materia Medica Vol1", by George B. Wood. Also available from Amazon: Part 1 and Part 2.
This is the rind of the lemon, which is the fruit of a variety of Citrus medica, a native of Asia, but now cultivated throughout the civilized world, cither in the open air, or in conservatories. It has the same aromatic properties as orange-peel, though less agreeable, and is employed for the same purposes.
The Volatile Oil of Lemons (Oleum LImonis, U. S., Br.) is often obtained from the fresh rind, either by distillation or pressure; that procured in the latter method having more exactly the odour of the rind, though the former is more clear. It is used to impart an agreeable flavour to other medicines, for which purpose a drop or two may be added to a fluidounce of a liquid for internal use, and ten drops to an ounce of unctuous matter for outward application. It has been employed, undiluted, as a local application to the conjunctiva, in affections requiring stimulation; being pressed from the fresh peel directly into the eye. It produces, however, excessive pain, and should be used with caution.
A Spirit of Lemons (Spiritus Limonis, U. S.), prepared by the U. S. Pharmacopoeia from lemon-peel, with the addition of the volatile oil of lemons, by maceration in alcohol, and a Tincture (Tinctura LImonis, Br.), prepared in the same manner from the fresh peel, may be used as grateful additions to bitter and laxative infusions and mixtures.