MUSTARD. The varieties of mustard-seed of commerce are produced from several species of the genus Brassica (family Cruciferae). Of these the principal are the black mustard, Brassica nigra (Sinapis nigra), the white mustard, Brassica alba, and the Sarepta mustard, B. juncea. Both the white and black mustards are cultivated to some extent in various parts of Eng land. The white is grown as a salad plant and has come into in creasing favour as a forage crop for sheep and as a green manure, for which purpose it is ploughed down when about to come into flower. The black mustard is grown solely for its seeds, which yield the condiment. When white mustard is cultivated for its herbage it is sown usually in July or August, after some early crop has been removed. In about six weeks it is ready either for feeding off by sheep or for ploughing down as a preparative for wheat or barley.
Brassica nigra occurs as a weed in waste and cultivated ground throughout England and the south of Scotland, and widely in the United States and Canada. It is a large branching annual 2 to 3 ft. high with stiff, rather rough, stem and branches, dark green leaves ranging from lyrate below to lanceolate above, short racemes of small bright yellow flowers one-third of an inch in diameter and narrow smooth pods. B. alba is more restricted to cultivated ground in Great Britain and has only sparingly es caped from cultivation in the United States ; it is distinguished from black mustard by its smaller size, larger flowers and seeds, and spreading rough hairy pods with a long curved beak.
The pungency and odour to which mustard owes much of its value are due to an essential oil developed by the action of water on two chemical substances contained in the black seed. These bodies are a glucoside (see GLUCOSIDES) termed by its discoverers myronate of potassium, but since called sinigrin, C1oH18KNS2O1o, and an enzyme, myrosin. The latter substance in presence of water acts on sinigrin, splitting it up into the essential oil of mustard, a potassium salt, and sugar. It is worthy of remark that
this reaction does not take place in presence of boiling water, and therefore it is not proper to use very hot water (above i2o° F) in the preparation of mustard. Essential oil of mustard is in chemical constitution an isothiocyanate of allyl The seed of white mustard contains in place of sinigrin a peculiar glucoside called sinalbin, C30H44N2S2016, in several aspects analogous to sinigrin. In presence of water it is acted upon by myrosin, present also in white mustard, splitting it up into acrinyl isothiocyanate, sulphate of sinapin and glucose. The first of these is a powerful rubefacient, whence white mustard, although yielding no volatile oil, forms a valuable material for plasters.
Both as a table condiment and as a medicinal substance, mustard has been known from a very remote period. Under the name of vary it was used by Hippocrates in medicine. The form in which table mustard is now sold in the United Kingdom dates from 172o, about which time Mrs. Clements of Durham hit on the idea of grinding the seed in a mill and sifting the flour.
The volatile oil distilled from black mustard seeds after macera tion with water is official in the British Pharmacopeia under the title Oleum sinapis volatile. It is a yellowish or colourless pungent liquid, soluble only in about fifty parts of water, but readily so in ether and in alcohol. From it is prepared, with camphor, castor-. oil and alcohol, the linimentum sinapis. Used internally as a condi ment, mustard stimulates the salivary but not the gastric secre tions. It increases the peristaltic movements of the stomach very markedly. One drachm to half an ounce of mustard in a tumblerful of warm water is an efficient emetic, acting directly upon the gastric sensory nerves, long before any of the drug could be absorbed so as to reach the emetic centre in the brain. The heart and respiration are reflexly stimulated, mustard being thus the only stimulant emetic.