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.
Wormwood, as a medicine, consists of the leaves and flowering tops of Artemisia Absinthium, the common wormwood of our gardens, but a native of Europe. It has a strong, peculiar odour, and an extremely bitter, disagreeable, nauseous taste. These properties, as well as its medical virtues, it imparts to water and alcohol. They reside chiefly, if not exclusively, in a bitter principle called absinthin, and a peculiar volatile oil, which, when separated by distillation with water, has a deep-green, brown, or yellowish colour, an acrid, bitter taste, and a strong odour of the plant. The herb may contain a little tannic acid, but not enough sensibly to modify its effects.
Wormwood is a stimulating tonic, resembling chamomile in its effects, but stronger and more disagreeable. In small doses, it operates like the simple bitters; in larger, excites the pulse, increases the heat of the skin, produces headache, and is said sometimes to have exhibited narcotic effects. Its active principles are no doubt absorbed, as it renders the flesh and milk of animals fed with it bitter. In very large doses it is apt to vomit. It is among the medicines used by the ancients, and, before the discovery of Peruvian bark, was much relied on in the treatment of intermittents. Though greatly inferior in antiperiodic power to cinchona, it has some efficacy in arresting intermittent fevers, and is particularly recommended as a preventive. It has been used also as an anthelmintic and emmenagogue, and probably has some efficiency in these respects. It is probably not without a stimulant influence over the nervous system, such as characterizes the antispasmodics, or nervous stimulants of the classification adopted in this work; and hence may be used, with hope of benefit, in hysterical cases attended with feeble digestion, and defective menstruation.
The dose of the powder is one or two scruples; that of the infusion, made in the proportion of an ounce to the pint, is two fluidounces. The herb has been used externally with hot water as a fomentation, but probably with little other benefit than such as may be ascribed to the heat and moisture.
A cordial is much used in France under the name of absinthe. It is said to be prepared by mixing about five drachms of the volatile oil of wormwood (essence d'absinthe) with 100 quarts of alcohol. It might be supposed that, in so small a proportion, the oil could produce no seriously injurious effects; but M. E. Descaine has satisfied himself that the cordial is much more marked in its effects, and much more injurious than the spirit contained in it can be; intoxication being more rapidly produced; the phenomena included under the name of alcoholism, both acute and chronic, more quickly developed; and the effects on the nervous system more marked, resembling those of the acrid narcotic poisons. (Comples Rendus, A out, 1864.) In confirmation of the statements of M. Descaine, M. Marce made various experiments with the lower animals, from the result of which it appears that the oil of wormwood is in large doses a violent narcotic poison. In the dog two or three grammes (30 to 45 grains) caused trembling, stupor, and insensibility, three or four grammes, epileptic convulsions, involuntary evacuations, foaming at the mouth, and stertor. But these symptoms were transient, and death did not result. (Bullet. Gen. de Therap., Mai 15, 1864).