338 SUBTERRANEAN ORGANS 



The student should observe 



(a) The curved rhizome with wiry roots, 

 (6) The characters of the transverse section, 

 (c) The scars of cataphyllary leaves. 



Constituents. Arnica rhizome contains about 0'5 per cent, of 

 volatile oil, and a bitter and acrid principle, arnicin, which has been 

 obtained in the form of a minutely crystalline yellow powder. It also 

 contains tannin, but no starch, the reserve material being inulin, the 

 latter character being useful in distinguishing it from any starch- 

 forming rhizome. The drug yields about 8 per cent, of ash. 



Uses. The tincture diluted with water is a popular application 

 for bruises, preventing swelling and hastening the absorption of 

 effused blood. It appears to increase the activity of the circulation 

 in the skin, but should be used with caution, as it is liable to produce 

 extensive dermatitis. 



Arnica is not often given internally ; it has a depressing or, in 

 over doses, irritant action, causing vomiting, pain, and purging. 



Substitutes, &C. Foreign roots and rhizomes are occasionally 

 present in the drug as imported, and have to be separated by hand- 

 picking. Amongst these may be mentioned the erect rhizome of the 

 common avens (Geum urbanum, Linne), which has an odour recalling 

 cloves, and the rhizomes of species of Hieracium, which have no oleo- 

 resin ducts. 



DANDELION ROOT 



(Radix Taraxaci) 



Source, &C. The common dandelion, Taraxacum officinale, Wiggers 

 (N.O. Composite), is widely distributed over Europe, Asia, and 

 North America, and is in many cultivated districts a troublesome 

 weed. In this country it has long been used as a domestic 

 medicine. 



The fresh root alone is official and is directed to be gathered in 

 the autumn, when, judging from analogy, it may be expected to be 

 most active. This, however, has been denied, the assertion being 

 made that the root is most active in the spring or summer. A method 

 for the quantitative determination of the active constituent not being 

 at present known, this point cannot be definitely settled, but roots 

 collected in the spring or summer contain much sugar, which is more 

 objectionable than inulin, so that, unless positive evidence can be 

 adduced to the contrary, the autumn must be regarded as the proper 

 season in which to collect dandelion root. 



