36 LEAVES 



than the Alexandrian, varying usually from 2'5 to 5 cm. in length. 

 They differ also in being more uniformly lanceolate in shape, less 

 conspicuously asymmetrical and less pubescent. They are some- 

 what firmer in texture than the Alexandrian, and are consequently 

 less broken when they arrive, and, being exported in compressed 

 bales, are usually flatter. There is also a slight but perceptible 

 difference in the odour of the two varieties. The student should 

 carefully compare these two varieties of senna. It is, however, 

 quite possible to select from the two varieties exceptional leaves 

 that are indistinguishable from one another. The student must be 

 guided by the characters of the majority. 



FIG. 24. Tinnevelly Senna leaves. Natural size. 



Constituents. The constituents of Tinnevelly senna are identical 

 with those of Alexandrian senna. Either variety may be used in 

 making the official preparations of senna. 



CHERRY-LAUREL LEAVES 



(Folia Laurocerasi) 



Source, &C. The cherry-laurel, Prunus Laurocerdsus, Linne (N.O. 

 Rosacece), is an evergreen shrub indigenous to Persia and Asia Minor 

 but cultivated in most temperate regions. It was introduced into 

 this country towards the end of the sixteenth century, but the 

 poisonous property of the water distilled from the leaves was not 

 known till 1731 ; the poisonous principle contained in it was identified 

 as hydrocyanic acid soon after the discovery of the latter by Scheele 

 in 1782. 



Description. Cherry-laurel leaves which are official in the fresh 

 state only, average about 15 cm. in length by 5 cm. in breadth. The 



