Active Ingredients. - A very important question, since great mistakes have been occasioned by erroneous views. The ingredient long supposed to be of most consequence is arnicine, C20H30O4, a bitter principle, which is insoluble in water, but freely soluble in alcohol and in ether, and forms amorphous masses of a golden yellow color; or else the ethereal oil, which is also insoluble in water. For a variety of reasons, hereafter to be mentioned, it is now probable that neither arnicine nor the oil, but "trimethylamine," is the really useful ingredient of arnica. Trimethy-lamine, C3H9N, is a clear, colorless fluid, which boils at a very low temperature, and then emits a fishy smell. It is quite freely soluble in water, in alcohol, and in ether, and its vapor is absorbed by water with great avidity. It has a strong alkaline reaction, and readily ignites, on the application of flame, even when diluted with an equal quantity of water.

Physiological Action. - The physiological action of trimethy-lamine, or of concentrated aqueous solutions of arnica, which contain trimethylamine, without arnicine, is as follows: Placed in simple contact with the skin, neither of these excites irritation; but if either of them be rubbed in for some time with flannel, the surface will become reddened. Like ammonia, they dissolve the little plugs of fat at the orifices of the sebaceous ducts. Applied to the mucous membrane, they act in a stimulant and caustic manner: pure trimethylamine is a decided caustic to mucous membranes. Taken internally, in large doses, it greatly reduces both the frequency and the force of the pulse, and causes a burning in the throat and stomach, but no sweating, no diuresis, no colic, and no diarrhoea. A drop of pure trimethylamine placed upon the lip, produces burning and a flow of saliva: the mucous membrane is first reddened, and then the epithelium is cast off, leaving a slight sore.1

The statements concerning the actions, both physiological and therapeutic, of trimethylamine, have been very various, as have been those respecting arnica itself. Buchheim, for example, regarded it as a substance of little power; but the recent experiments of Dujardin-Beaumetz - one of the highest living authorities upon the action of drugs - seem to render it clear that trimethylamine has a very definite physiological action, and that among other things, it diminishes the excretion of urea. And we shall see presently that he speaks most highly of it as a remedy. Trimethylamine, as employed by M. Beaumetz, was prepared either from herring-brine or from human urine, both of which fluids yield it to chemical processes. The external effect of arnica involves important questions, for while it is known that many persons have found it an excellent application for bruises and for wounds, other observers have complained that it produces either an actual erysipelas, or a peculiar violet-colored eruption, attended by great heat and pain. I venture to affirm that these are physiological consequences of the alcoholic, and not of the aqueous solution, which latter contains neither arnicine nor the oil. I have never seen inflammatory consequences follow the application of the purely aqueous lotion to wounds or bruises.

Therapeutic Action. - Arnica, which has always been so favorite a medicament with the homoeopathists, is a remedy much older than homoeopathy, and some of the most valuable evidence in its favor has been given by non-homoeopathic physicians. Among the most interesting of these testimonies is that of Schroder Van der Kolk, who employed it largely in the form of infusion of the flowers and of decoction of the root.

Mental Diseases were the field upon which Van der Kolk chiefly tested the powers of arnica. He employed the infusion of the flowers in the milder cases; and the decoction of the root when a more powerful remedy was required. He found arnica invaluable in that condition of idiopathic mania where the first excitement having diminished, the head nevertheless remains hot, and where a tendency to imbecility or to paralysis is shown. Exhausting diarrhoea and general cachexia are also checked by arnica with great certainty. Van der Kolk's results are the more interesting because obtained with aqueous preparations.

Guibert.

In Paralytic Affections of various kinds, arnica has been found useful by numerous observers, among whom are Alibert and Meyer, who by means of it cured paralyzed bladder. Mannoir employed it with success in amaurosis, for which disorder it has long been a popular remedy in Germany.

In Typhoid and Typhus Fevers, arnica has been very highly extolled, though one of the latest writers, Nothnagel, speaks of it disparagingly. He does not, however, advance any good reasons for this, and as he allows that the general "picture" of the physiological actions of arnica gives every indication of the existence of a substance which has definite powers as a remedy, we may fairly put against his rather vague opinion, and against the prejudice which British physicians have widely felt (chiefly because of its repute with "homceopathists"), the very large body of German and French experience which exists as to the action both of arnica and, in more recent days, of trimethylamine.

In Rheumatism there has always been good evidence of the utility of arnica. Even in England, Dr. Fuller has spoken strongly of the value of the tincture and of the infusion in rheumatic gout. But the investigations concerning trimethylamine have given a new and important turn to the subject of arnica. As long ago as 1854, Awenarius employed trimethylamine in acute rheumatism. In the course of three years he treated 213 hospital patients, besides many in private practice. He frequently found the joint-pain and the fever arrested in a single day's treatment. Guibert confirmed the utility of trimethylamine in acute rheumatism. On the other hand, many observers denied (and still deny), its efficacy, and during several years very little was heard of the remedy. But the recent researches of M. Beaumetz have attracted general attention to the matter; the results attained by him being very remarkable. It should be mentioned that for a long time there was a confusion between the real trimethylamine and an isomeric body, "propylamine," which was conclusively proved, however, by Winckler and Mendius (1854 - 1857) to possess different physical and chemical qualities. Under the name of propylamine various commercial samples have been sold, of different composition in detail, but all containing alkalies, ammonia, and trimethylamine. On account of the impurity and variableness of these preparations, Beaumetz determined to employ a definite salt, the hydro-chlorate of trimethylamine. This substance crystallizes in long needles; is very deliquescent, and its solution, when very concentrated, acts as an irritant to the skin and the mucous membranes. Its solution does not possess the stinking-fish smell of trimethylamine unless it be heated or mixed with an alkali.

M. Beaumetz ascertained, by experiments upon himself, that this salt has the power to distinctly slow the pulse, and to diminish the bodily temperature. Its action as a sudorific, or as a diuretic, is very irregular, and corresponds pretty closely with what is known, in these respects, of ammoniacal salts. But its effects, as tested in rheumatic fever, are remarkably uniform and striking in the following respects: lowering of pulse and temperature, relief of the articular pain and swelling, and diminution of the excretion of urea. In the last particular, the effects of the drug are shown in an elaborate table of urine-analysis in a case where the urea-discharge (commencing at 40.74 grams per diem) was reduced in six days to 8.55 grams per diem. The doses employed by M. Beaumetz were from 7.8 to 15.6 grams in 24 hours, in solution. I believe the best vehicle is about a tablespoonful of water to each dose. These quantities of the drug cause no irritation of the throat or stomach.

In Inflammations of the Serous Membranes, Awenarius and others have obtained excellent results with trimethylamine; but it must be confessed that these require the confirmation of more extended experience.

The only preparation of arnica recognized by the British Pharmacopoeia is the alcoholic tincture; and herein, for reasons already stated, it is evident that a great mistake has been committed. But the tincture has special virtues of its own. It is very probably more tonic and stimulating than other preparations, as containing not only trimethylamine, but also arnicine and the ethereal oil. Quite possibly, also, the latter ingredient, besides being stimulant to general nervous power, may be sedative, like chamomile oil, etc., to hyper-excited reflex irritability.

For External Bruises and Cuts, arnica is undoubtedly very useful; and, as already observed, the mischances that have attended its use, have probably resulted from the fact that the tincture containing arnicine and the volatile oil has been employed. The infusion or decoction alone should be used; and it would be better to give up employing all liniments and lotions in which the tincture is present.

For Internal Bruises, arnica is a most excellent remedy, neutralizing the ill effects of blows, falls, and other mechanical injuries. Ecchy-mosis and sanguineous effusions are rapidly dispersed by it, provided the medicine be administered shortly after the injury has been sustained. In cases of shake, concussion, and shock, resulting from railway accidents, it is also very serviceable. Under these circumstances I recommend that 5 to 10 minims be taken every 2 or 3 hours in a wineglassful of water. I believe there is no drug that can so well restore the contused muscular fibre to its healthy condition in a short space of time as arnica; and I consider it a great pity that it has not come into more general use in cases of this description. When used after amputations, arnica certainly has the power of uniting the surfaces very rapidly.

In Haemorrhages arising from mechanical violence, bleeding from the nose, and haemoptysis, arnica is also of great service; and the same may be said of pulmonary congestions arising from fractured ribs. In cases of concussion of the brain, induced by a fall, I cannot speak too highly of it.

As an Electuary, the dried and pounded flowers, mixed with honey or syrup, are sometimes used. A weak infusion may also be employed for this purpose, especially in chronic dysentery. When the motions are slimy and purulent, and attended by tormina and cutting pains in the bowels, the tincture may be given internally with good effect.

Preparations and Dose. - Extractum Arnicae, gr. ij. - v. (.13 - .32); Tinct. Arnicae, m v. - xx- (.30 - 1.20); Emplastrum Arnicae.