Active Ingredients. - For so familiar a substance as it is, mustard has a rather complex chemistry.

(a) The fixed oil, which forms about 25 per cent., can be obtained from either white or black mustard by expression of the ground and sifted seeds. It is almost devoid of acridity, but has been used as a purgative and vermifuge. It would possess little interest, but for the fact that it contains -

(b) Erucic or brassic acid, C22H42O2. This is a crystalline body, forming long, slender needles, insoluble in water, but highly soluble in alcohol and ether. At present it is not known that erucic acid possesses any marked physiological properties.

(c) Myronic acid, C10H19NS2O10, exists in black mustard-seeds in the form of myronate of potash, C10H18KNS2O10. This myronate of potash is easily soluble in water, insoluble in ether, chloroform, and benzol, some what soluble in dilute alcohol: it has a cool, bitter taste and neutral reac tion; when heated, it gives out a pungent smell.

(d) Myrosine is an albuminoid substance analogous to emulsin, and acts as a ferment to the myronic acid in mustard-seeds, as soon as water is mixed with the flour. By this reaction is produced -

(e) The volatile oil of mustard, which has no existence in the dry seeds. It is colorless or light yellow; has a pungent odor and taste, and a neutral reaction. It largely consists of the sulpho-cyanide of allyl, C4H6NS, mixed with some cyanide of allyl. It is almost, if not quite, identical with a similar oil obtained from horse-radish.

White mustard-flour, like black, also undergoes a fermentation process, when mixed with water; but the oil developed, which is of a pungent character, is not the volatile oil of black mustard.

(f) Sinapine, C16H13NO5, exists in both white and black mustard-seeds, under the form of the sulpho-cyanide. Sinapine is not to be obtained pure in a solid form, but can be procured as a watery solution, indirectly, through the medium of its bisulphate, which, again, can be got by adding concentrated sulphuric acid to hot alcoholic solution of the sulpho-cyanide. The watery solution of sinapine has a marked alkaline reaction, and a light-yellow color; but, during evaporation, it changes through green and red, and at last leaves a residue which is of a brown color and non-crystalline.

Physiological Action. - The well-known irritant and acrid qualities both of white and black mustard-seeds are dependent on the fermentation products, already described, which are the result of the mixture of mustard with water. The volatile oil of black mustard, ascending in the steam of hot water which is poured on mustard-flour (as in a mustard foot-bath), acts either as an irritant (causing sneezing, watering of the eyes, etc.), or, if the vapors be not too strong, as a soporific. The local irritant effects of mustard and water on the stomach and bowels are well known; carried to excess, they end in gastro-enteritis. Mustard-flom mixed with water and applied to the skin produces effects of the same kind as cantharides; proceeding to vesication, and even to ulceration and gangrene, if pushed to an extreme. The main difference of mustard irritation from cantharides irritation is that the former subsides more quickly.

The irritant qualities of the volatile oil have been thoroughly tested. It is one of the most poisonous of the ethereal oils: rabbits have been killed in two hours by a drachm, and in fifteen minutes by half an ounce; there was violent gastro-enteritis, and the odor of the oil was perceptible in the blood, the urine, and the breath. Upon the human skin the volatile oil acts with excessive severity, causing great burning pain, with redness and rapid vesication, even when much diluted.

Therapeutic Action. - Mustard has been administered and applied in many forms. As to its internal use, we may first mention the old practice of administering the uncrushed seeds, which has received support in recent years. It has been shown 1 that mustard-seeds by no means act (as had been asserted) merely as mechanical irritants. On the contrary, in their somewhat slow passage along the alimentary canal they swell up and become mucilaginous (especially white mustard-seeds, of which the external coating is thin), and then give out the true acrid products of the fermentation of myronic acid and myrosine. It is urged that from the slow and equable manner in which this takes place, we have, in uncrushed mustard, a singularly effective and manageable stimulant to all the functions of the alimentary canal. But the objection is that the seeds are apt to accumulate in some one place, as the appendix vermifor-mis, and then produce dangerous inflammatory effects. Otherwise, there can be no doubt that both laxative and diuretic effects can be produced in this way.

As an emetic, a tablespoonful of mustard-flour in warm water is one of the readiest and best; it is especially indicated in cases where it is desired to stimulate the action of a failing heart, whether in ordinary diseases, in narcotic poisoning, in the collapse of cholera, or in certain forms of paralysis.

It is probable that, in future, mustard, when administered internally as a tonic stimulant, in cases of dyspepsia with torpid liver and loss of appetite, would be best employed in the form of alcoholic solution of the volatile oil. In the Austrian army they have even substituted the oil for mustard advantageously for dietetic purposes. The solution of 24 drops of the oil to the ounce of spirit, as originally recommended by Meyer and Wolff, is an excellent and powerful medicine both in chronic catarrhal dyspepsia and chronic bronchial catarrh (in doses of three to five drops in some emulsion): it has also received much praise as a diuretic in dropsy, but the special indications for its use in the latter way have not been defined.

The distilled water of mustard-seed has been employed in cases of itch.

The principal use of mustard is, however, in the form of poultice, or cataplasm. In various affections of the brain, such as the stupor and delirium of low fever, apoplexy, and in cases of poisoning by opium, or other narcotics, it is most valuable, and should then be applied to the feet and ankles; operating on the principle of a blister, its speedy operation giving it a great advantage over the blister similarly formed by cantharides. So, too, in pulmonary and cardiac affections, the poultice may be applied to the chest of the patient with a certainty of the most beneficial effects resulting. Mustard poultice is excellent again as a counter-irritant in inflammation, in neuralgic pains, and in spasms, as well as in pleurodynia, and arrested catamenia.

1 Journal de méd. de Bruxelles, tome 50, 1870, p. 260. Paper by M. Commailhe.

Preparations And Dose. - As an emetic, from a teaspoonful to a tablespoonful of the ground seed mixed with warm water. It is, however, seldom used for this purpose except in emergencies or in cases of narcotic poisoning.