ACTIONS AND USES 577 



the epidermis ; 4 of inorganic matters, and 10 to 15 of 

 myrosin, a ferment similar to diastase or the emulsin of 

 bitter almonds, usually more abundant in white than in 

 black mustard seeds, and coagulated and rendered inactive 

 when heated above 140 Fahr. Black mustard, besides, 

 contains about 2| per cent, of the crystalline potassium 

 myronate or sinigrin ; white mustard contains an allied 

 principle, sinalbin. When dissolved in water, as in making 

 mustard flour into paste, the ferment myrosin decomposes 

 the crystalline bodies, and there are produced two acrid, 

 irritant oils the pungent volatile oil of mustard, allyl- 

 isothiocyanate (C 3 H 5 NCS) from the black mustard, and 

 the fixed oil acrinyl-isothiocyanate (C 8 H 7 NSO) from the 

 white mustard. 



ACTIONS AND USES. Unbruised mustard-seeds, being only 

 partially and gradually digested, have little effect when 

 swallowed. When the ground seeds are mixed with water 

 the pungent, acrid oils are evolved ; large doses of the flour 

 are accordingly irritant ; medicinal doses are stomachic, 

 carminative, and stimulant. It is, however, rarely used 

 internally, excepting as a locally acting emetic for the dog, 

 cat, or pig. For this purpose a dessert-spoonful of mustard 

 flour is given, dissolved in several ounces of water. Small 

 doses are slightly laxative and diuretic ; whilst large doses 

 may cause purging and collapse. 



As an external irritant, mustard is much used as a rube- 

 facient and vesicant. The paste made with cold water, and 

 rubbed into the skin of the horse, within twenty minutes 

 causes congestion, heat, and tenderness, with subsequent 

 swelling. Reflexly, the activity of conterminous and sub- 

 jacent parts is roused. In two to six hours vesication occurs ; 

 twenty-four hours later some of the vesicles will have run 

 together, others being ruptured. From repeated, prolonged, 

 or injudicious use in irritable states of the skin, there 

 occasionally ensue active inflammation, sloughing, and 

 destruction of the hair-roots. 



Compared with cantharides, mustard acts more promptly, 

 but unless used freely or repeatedly it is less permanent. 

 It is used to control functional disturbance rather than to 

 repair structural damage ; it causes more swelling of sur- 



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