38 LEAVES 



Fresh leaves from healthy plants yield on an average about O'l per 

 cent, of hydrocyanic acid. In the autumn the yield is less than 

 in the spring or early summer, the young leaves being especially 

 rich in prulaurasin ; newly unfolded leaves have yielded as much as 

 2-49 per cent, of hydrocyanic acid (Ven, 1898). 



Prulaurasin resembles but is not identical with amygdalin. By acting 

 upon amygdalin with yeast Fischer obtained an amygdonitrile glucoside, 



CN 



C 6 H_.CH < r . J " n TT ~ This body is isomeric with prulaurasin, but differs 

 O.'-tLl* 





in its optical rotation ( 26-9), and yields, when acted upon by hydrochloric 



OTT 

 acid, Isevo -phenylglycollic acid (mandelic acid), C 6 H 5 .CH <TT * Under 



similar conditions prulaurasin yields inactive (racemic) phenylglycollic acid 

 Hence prulaurasin is the glucoside of racemic phenylglycollic acid, and the 

 amygdonitrile glucoside that of Isevo -phenylglycollic acid. Sambunigrin, an 

 allied glucoside contained in the leaves of the elder, is the glucoside of dextro- 

 phenylglycollic acid. Both the amygdonitrile glucoside and sambunigrin are 

 readily converted into prulaurasin by dilute alkalies. 



Several other glucosides have been discovered (e.g. manihotoxin, lotusin, 

 dhurrin, phaseolunatin, gynocardin, linamarin, corynocarpin) which under the 

 influence of enzymes yield hydrocyanic acid ; they are collectively termed 

 * cyanogenetic ' glucosides. 



Uses. Cherry-laurel water is employed as a sedative, its action 

 being due to the hydrocyanic acid it contains. 



WITCH-HAZEL LEAVES 



(Folia Hamamelidis) 



Source &C. The witch-hazel, Hamamelis virginiana, Linne (N.O. 

 Hamamelidece) , is a common shrub in the United States and Canada. 

 It attains a height of about 3 metres, and resembles the common hazel 

 both in its leaves and in its fruit, which is edible. Both the fresh 

 and dried leaves are official, the former being employed for the prepara- 

 tion of Liquor Hamamelidis. The bark is also used in medicine. 



Description. Commercial witch-hazel leaves are usually in a 

 somewhat indifferent state of preservation, being frequently dis- 

 coloured, broken, and pressed together into more or less compact 

 masses. Well-preserved full-grown leaves are of a dark green or 

 brownish green colour, and attain 15 cm. in length by 10 cm. in 

 breadth. They are broadly oval or rounded- obovate, the lamina 

 tapering somewhat towards the base, where it is decidedly oblique, 

 usually cordate, and provided with a short petiole ; the apex is 

 acuminate, but is often imperfect and then frequently obtuse. The 

 margin is coarsely crenate or even sinuate. On the under surface 



