21 COCHLEABJA ARMORACIA 



Colour. Pale yellowish- or Colour. Coffee-coloured, or 



brownish- white externally. more or less distinctly earthy - 



brown externally. 



Odour. Especially developed Odour. Merely earthy, 

 upon being scraped, when it is 

 very pungent and irritating. 



Taste. Very pungent, and Taste. At first slightly bit- 

 bitter or sweet according to ter, but afterwards producing a 

 circumstances. disagreeable tingling and numb- 



ness. 



Since the publication of the above paper, and the marked 

 attention which was called to this highly dangerous substitution, 

 no further accidents have taken place ; it is hoped, therefore, that 

 now the great differences between the two roots have been 

 pointed out it will not again occur. 



The chemistry of horseradish root has not as yet been accurately 

 determined. It is certain, however, that it owes its properties 

 essentially to the formation of a volatile oil which may be 

 obtained from it by distillation with water. This oil was proved by 

 Hubatka, as far back as 1843, to be identical with the volatile 

 oil obtained under like circumstances from black mustard seeds. 

 The volatile oil does not therefore pre-exist in horseradish root, 

 but is developed like that of black mustard from the mutual 

 reaction of sinigrin and myrosin in the presence of water, as 

 described under Brassica (Sinapis) nigra. This process, accord- 

 ing to the authors of Pharmacographia, " does not go on in the 

 growing root, perhaps because the two principles in question are 

 not contained in the same cells, or else exist together in some 

 condition that does not allow of their acting on each other, 

 a state of things analogous to that occurring in the leaves of 

 Lauro-cerasus." It should, however, be noted that the presence 

 of myrosin is inferred to be one of the constituents of horse- 

 radish root, rather than proved. The amount of volatile oil 

 thus obtained by the distillation of fresh horseradish root with 

 water is very small, averaging only about 0*2 per cent. 



Medical Properties and Uses. It has the same properties as 



