WHITE MUSTARD 149 



them with water, and note that the taste is pungent, but the odour 

 is not. He should also observe : 



(a) The minutely pitted surface, 



(b) The incumbent, folded cotyledons. 



Constituents. White mustard seeds contain a fixed oil (about 

 30 per cent.), mucilage (in the epidermis of the seed-coat), and proteids 

 (about 25 per cent.). Starch is not present in the ripe seeds, which 

 yield about 4 per cent, of ash. 



They contain, in addition, a crystalline glucoside, sinalbin, and 

 the same enzyme as is found in the black mustard seed viz. myrosin. 

 Sinalbin is readily soluble in water and in boiling alcohol, but only 

 very sparingly in cold alcohol ; it assumes an intense yellow colour 

 when acted upon by alkalies. Under the influence of myrosin, and 

 in the presence of water, it yields acid sinapine sulphate, dextrose, 

 and acrinyl isothiocyanate. The decomposition may be represented 

 by the following equation : 



C 30 H 44 N 2 S 2 16 = C 7 H 7 O.N:C:S + C 6 H 12 O 6 + C 16 H 24 N0 5 HS0 4 . 



Sinalbin Acrinyl isothiocyanate Dextrose Acid sinapine sulphate 



Of these three substances, acrinyl isothiocyanate is a yellow oily 

 liquid with a pungent taste and powerful rubefacient action, but as it 

 is not volatile it is destitute of pungent odour or pungent effect on 

 the eyes. In this particular the pungent principle obtained from 

 white mustard di r ^s essentially from that yielded by black, and 

 since this principle is not volatile, it is evident that volatile (or essential) 

 oil of mustard cannot be obtained from white mustard seeds. It 

 is very remarkable, considering the close relationship of the two 

 plants and similarity in other constituents, that white mustard should 

 contain no sinigrin and black no sinalbin. 



Sinapine is an alkaloid which is so unstable that it has not yet been 

 isolated ; the acid sulphate and other salts are crystalline and assume 

 a bright yellow colour in contact with alkalies. 



Uses. White mustard possesses rubefacient and vesicant properties 

 similar to those of black mustard. 



LINSEED 



(Flax Seed, Semina Lmi) 



Source, &c. The flax plant, Linum usitatissimum, Linne (N.O. 

 Linece), is a tall, erect annual, spread by cultivation over all tem- 

 perate and tropical regions. Not only has the plant been known and 

 cultivated for so many centuries that its geographical origin cannot 

 be identified, but the use of its fibre can be traced back to the thir- 

 teenth or fourteenth century before the Christian era. Flax seeds, 



