56 LEAVES 



German digitalin is amorphous and said to consist chiefly of digitalein. 



Digitalinum verum is amorphous and said to be the best variety of digitalin 

 for medicinal use. 



Several other species of Digitalis have been examined ; all were found to be 

 toxic. 



Uses. Foxglove increases the activity of muscular tissue, especially 

 that of the heart and arterioles, and is employed in most forms of 

 cardiac failure. Digitoxin is cumulative, and the action of prepara- 

 tions of foxglove must therefore be watched. 



Assay. Since the therapeutical activity of foxglove leaves is due to more 

 than one glucoside, it is obviously impossible to assay the leaves by determining 

 one only of these, e.g. digitoxin. No method of determining digitalein or digitalin 

 is known. Hence chemical methods of assay fail, and recourse must be had 

 to the physiological assay (compare p. 168). 



Adulterations. Leaves of D. Thapsi, Linne, imported from Spain ; 

 greyish green or yellowish green, lamina less decurrent, hairs very 

 numerous, long, curling. Said to be more toxic than D. purpurea. 



Mullein leaves ( Verbascum Thapsus, Linne) ; woolly ; hairs branched. 



Comfrey leaves (Symphylum officinale, Linne) ; lanceolate or ovate ; 

 isolated stiff hairs. 



Primrose leaves (Primula vulgaris, Hudson) ; nearly spathulate ; 

 lateral veins straight, dividing near the margin. 



Ploughman's spikenard (Inula Conyza, de Candolle) ; margin either 

 entire or dentate, with horny points to the teeth. 



Elecampane leaves (Inula Helenium, Linne) ; lower lateral veins 

 not decurrent. 



LAUREL LEAVES 



(Folia Lauri) 



Source, &c. The true laurel, bay or bay laurel, Laurus nobilis, 

 Linne (N.O. Laurinece), is a small evergreen tree commonly cultivated 

 in this country. 



Description. Laurel leaves are of a shining, green colour on the 

 upper surface, paler below, coriaceous in texture, lanceolate and 

 acuminate in outline, attaining 10 cm. or more in length and shortly 

 stalked, with an entire, wavy margin, the apex being often acute 

 but sometimes blunt. They are quite glabrous, with the exception 

 of a few hairs often present on the under surface in the angles made 

 by the lateral veins with the midrib. The upper surface appears 

 finely shagreened ; the lower is reticulated, an appearance due to 

 the prominence of the network of minute veinlets. When crushed 

 they emit an aromatic odour, due to the volatile oil contained in oil- 

 cells situated in the mesophyll of the leaves. These oil-cells are with 



