DIGITALIS GLUCOSIDES 535 



probably the same properties as the D. purpurea, recognised 

 by the B.P. It is herbaceous, biennial or perennial, with 

 numerous drooping, purple-spotted, occasionally white 

 flowers, an erect stem one to five feet high, and large 

 alternate ovate-lanceolate, crenate, rugose leaves, downy, 

 especially on their paler lower surfaces, and tapering into 

 winged foot-stalks. Leaves of the second year's growth 

 are preferred as they are richer in the active principles. 

 The leaves are dried in baskets, in darkness, over stoves, 

 and are then of a dull-green colour, with little smell, but 

 a nauseous, bitter, slightly astringent taste. They should 

 be used when fresh ; twelve months' keeping greatly 

 diminishes their activity. Both the roots and seeds are 

 bitter, and probably active, but less so than the leaves. 



The chemistry of digitalis is still somewhat uncertain, 

 but the following active principles can be extracted : 



(1) Digitalin, or digitalinum, a bitter glucoside, almost 

 insoluble in water, but readily soluble in alcohol. Pure 

 digitalin and the commercial varieties are topical irritants 

 and muscle poisons, and hence notable cardiac poisons. 

 The three undermentioned non-nitrogenous substances have 

 also been isolated. 



(2) Digitoxin is a crystalline body, insoluble in water, but 

 soluble in ether, chloroform, and alcohol. It is the most 

 active of the several glucosides which constitute digitalin. 



(3) Digitalein is bitter and amorphous, and insoluble 

 in water. Soluble in alcohol, chloroform, and in acetic acid. 

 Digitoxin and digitalein act in the same manner as digitalin. 



(4) Digitonin is soluble in 600 parts of water, and in- 

 soluble in alcohol, benzine, ether, and chloroform (Kauf- 

 mann) ; resembles saponin, the active principle of quillaia, 

 the Chili soap bark ; is a powerful irritant, local anaesthetic, 

 and muscular paralysant ; and hence is in some degree 

 antagonistic to digitalin, digit oxin, and digitalein. 



These non-nitrogenous bodies, in very variable proportion, 

 are obtainable from the plant grown in different climates 

 and circumstances, and also from different parts of the same 

 plant. The tincture contains the first three in solution, 

 while the infusion holds them in suspension and thus is 

 an active preparation. They readily yield products of 



