96 



CEUCIFER^E. 



Constituents. — The white mustard-seed is about one-twelfth of an inch 

 in diameter, almost globular, and of a yellowish color ; the black mustard- 

 seed one twenty-fifth of an inch in diameter, similar shape, blackish- 

 brown. Both yield a yellow powder, and both contain a considerable 

 percentage of fixed oil, which is bland, inodorous, and non-drying. Their 

 active irritating constituents are, however, though similar, far from identi- 

 cal, that of black mustard being 

 a volatile oil, while that of white 

 mustard cannot be obtained by 

 distillation. In neither case 

 does the acrid principle pre-ex- 

 ist in the seed, but is formed by 

 chemical reaction or fermen- 

 tation of existiDg principles 

 when brought into contact with 

 each other in the presence of 

 water. The reaction differing 

 so widely in results in the two 

 cases is thus explained : Black 

 mustard has as one of its constit- 

 uents a crystallizable substance 

 termed sinnigrin, which in the 

 presence of another constituent, 

 myrosin, an albuminous body, 

 and water, is decomposed, yield- 

 ing sugar, bisulphate of potas- 

 sium, and the volatile oil of 

 mustard. White mustard, on 

 the other hand, though contain- 

 ing myrosin, has instead of sinnigrin a similar complex substance, termed 

 sinalbin, which is decomposed by myrosin in the presence of water, yield- 

 ing sugar, sulphate of sinapin, and sulphocyanate of acrinyl, the latter 

 being the acrid principle. 



Preparations. — Of white mustard, none ; of. black mustard, Charta 

 sinapis — mustard paper. — United States Pharmacopoeia. 



Medical Properties and Uses. — These are too well known to require 

 more than mere mention. As an aid to digestion it is used in every 

 household. As a prompt and efficient emetic it is almost always at hand 

 and the first to be employed in emergencies. As a rubefacient its sphere 

 of usefulness is practically unlimited. 



CAPSELLA. 



Capsella Bursa-pastoris Moench (Thlaspi Bursa-pastoris Linne). — 

 Shepherd's Purse. 



Fig. 109. — Brassica (sinapis) nigra. 



