590 Prof. H. E. Armstrong and Dr. E. F. Armstrong. [Apr. 29, 



The experiments to be described have been carried out with leaves of the 

 Cherry laurel {Prunus laurocerasus). These contain Frulaurasin* which 

 Caldwell and Courtauld have shown to be a mixture in equal proportions of 

 the two isomeric forms of mandelonitrile /S-glucoside, PhCH(CN)'0'C6Hn05.f 

 The glucoside is present not only in the leaves but also in the young stem and 

 the older wood and is always accompanied by an enzyme which can deter- 

 mine its hydrolysis ; the bursting buds in which the leaves are just beginning 

 to unfold are particularly rich in glucoside. 



The leaves were gathered during March and the earlier part of April ; they 

 were picked fresh for each experiment; care was always taken to select 

 uninjured leaves. 



In making an experiment, the leaf was placed in a test-tube provided with a 

 sound cork ; the " anaesthetic " in excess of the quantity required to saturate 

 the air in the tube or sufficient liquid to cover about one-half to two-thirds of 

 the leaf surface was then added and the tube corked ; a slip of slightly 

 moistened picrate paper was introduced together with the cork, which held it 

 in place above the leaf. In some cases, the end of the leaf stalk was sealed by 

 dipping it into molten paraffin wax. The tubes were either set aside at the 

 air temperature or incubated at 37°. 



In presence of chloroform, the yellow test paper became appreciably red 

 within half an hour at 37°, within about two hours at room temperatures and 

 within six to eight hours at 0°; the rate of change is therefore about doubled 

 by each 10° rise in temperature. 



JEjfcd of Vapours. — In our first series of experiments, we ascertained that 

 the various " anaesthetics " used could be grouped in classes in the following 

 manner, according to the degree of rapidity which they determined the libera- 

 tion of liydrogen cyanide : — 



Quickly Active. — Ammonia, carbon bisulphide, chloroform, toluene, ether, 

 amylic alcohol, ethylic alcohol, amylic acetate, ethylic acetate. 



Moderately (j[uicldy Active. — Benzene, naphthalene, thymol, acetic acid. 



Slowly Active. — Carbon dioxide, benzaldehyde, limonene. 



Observations were made witli most of these substances at room temperatures 

 as well as at 37°. Similar results were obtained by using in place of laurel 

 leaves flax &iiQ(i.Yu\g^ {Linum tisitatissimum) and currant leaves {liihcs ruhruni ) 



Hffcct of Solutions. — Sound leaves may' be from one-half to two-thirds 

 immersed in water at 37° (hiring four br five days or at ordhiary temperatures 

 during a uiuch longer i)eriod without hydrogen cyanide becoming apparent. 

 liiluLe solutions of most metallic salts .also produce no apparent effect when 



* H6ri88ey, ' Compt. Rend.,' 1905, vol. 141, ]>. \m. 

 t 'Chem. Soc. Trium.,' 1!K)7, vol. p. (wl. 



