=Chemical Composition=—Among the constituents of horse-radish root (the chemical history of which is however far from perfect) the volatile oil is the most interesting. The fresh root submitted to distillation with water in a glass retort, yields about ½ per mille of oil which is identical with that of Black Mustard as proved in 1843 by Hubatka. He combined it with ammonia and obtained crystals of thiosinammine, the composition of which agreed with the thiosinammine from mustard oil. An alcoholic extract of the root is devoid of the odour of the oil, but this is quickly evolved on addition of an emulsion of _White_ Mustard. The essential oil does not therefore pre-exist, but only sinigrin (myronate of potassium) and an albuminoid matter (myrosin) by whose mutual reaction in the presence of water it is formed (p. 66). This process 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_. By exhausting the root with water either cold or hot, the sinigrin is decomposed and a considerable proportion of bisulphate is found in the concentrated decoction. Alcohol removes from the root some fatty matter and sugar (Winckler 1849). Salts of iron do not alter thin slices of it, tannic matters being absent. The presence of myrosin, which at present has been inferred rather than proved, ought to be further investigated. The root dried at 100° C afforded 11·15 per cent. of ash to Mutschler (1878). =Uses=—An infusion or a distilled spirit of horse-radish is reputed stimulant, diaphoretic, and diuretic, but is not often employed. =Substitute=—In India the root of _Moringa pterygosperma_ Gärtn. is considered a substitute for horse-radish. It yields by distillation an essential oil of disgusting odour which Broughton, who obtained it in minute quantity, has assured us is not identical with that of mustard or of garlic. CANELLACEÆ. CORTEX CANELLÆ ALBÆ. _Canella Bark_, _Canella Alba Bark_; F. _Canelle blanche_; G. _Canella-Rinde_. =Botanical Origin=—_Canella alba_ Murray,[310] a tree, 20 to 30 or even 50 feet in height, found in the south of Florida, the Bahama Islands (whence alone its bark is exported), Cuba, Jamaica, Ste. Broix, Guadaloupe, Martinique, Barbadoes and Trinidad. =History=—The drug was first mentioned in 1605 by Clusius,[311] who remarks that it had been then newly brought to Europe and had received the name of _Canella alba_ (White Cinnamon). It was afterwards known as _Costus Corticosus_, _Costus dulcis_, _Cassia alba_, _Cassia lignea Jamaicensis_ or _Jamaica Winter’s Bark_. Dale[312] writing in 1693 notices it as not unfrequently sold for Winter’s Bark. Pomet[313] (1694) describes it as synonymous with Winter’s Bark, and observes that it is common, yet but little employed.