350 Prof. H. E. Armstrong and Mr. E. Horton. [Mar. 3, 



cyanide and is therefore allied to Fischer's glucoside in the manner shown in 

 the following formiike : — 



Me2C(CN).O.C6Hu05 PhHC(CN).O.C6Hu05 



The statements made with regard to this glucoside and the associated 

 enzyme by Dunstan, Henry and Auld in their several communications to this 

 Society* are of a very striking character. 



In their valuable summary account of the cyanoplioric glucosides, read at the meeting 

 of the British Association in York, in 1906, t Dunstan and Henry point out that the 

 enzymes found in P. lunatus seeds are of special interest. To quote almost their words : — 



The mixture prepared from the beans contains at least two enzymes, one of the 

 emulsin type and the other of the maltase type ; it is the latter which attacks phaseo- 

 lunatin. Examination of the dextrose produced by the hydrolysis of phaseolunatiu by 

 the maltase-like enx.vuie present in the beans shows that it is the a-isomeride, so that 

 phaseolunatiu is an a-glucoside and may therefore be represented as the a-dextrose ether 

 of acetonecyanohydrin. 



In order that these statements may be undei'stood, it is desirable to give a short account 

 of the work on which the}' are based. It appears that the glucoside termed phaseolunatin 

 by Dunstan and Henry, by whom it was de.scribed in 1903, was first isolated, in 1891, 

 from young flax plants, by Jorissen and Hairs, by whom it was termed Linanmrin — a 

 name for which, therefore, priority may be claimed. The statement made by Dunstan 

 and Henry, in 1903, was that the enzyme of Plvtseolus lunatus readily hydrolyses 

 amygdalin, salicin and phaseolunatin. As the latter was also hydrolysed by the emulsin 

 of sweet almonds, it was probable that the enzyme of Phaseolus lunatus is emulsin. 



Jori.ssen and Hairs, who examined the enzyme contained in tlax seedlings, found — to 

 <luote Dunstan — that whilst it had the property of hjdrolysing both linamarin and 

 amygdalin, the emulsin of almonds was incapable of decomposing linamarin. 



Jouck, however, states, in opposition to Jorissen and Hairs, that linamarin is decom- 

 posed by the emulsin of almonds. 



The enzyme extracted from flax seeds was found by Dunstan, Henry and Auld to 

 have a range of activities similar to that of the emulsin of almonds : it readily hydi"olyse(i 

 amygdalin and salicin. 



They wei-e led to conclude that probably the same enzyme is contained in Phaseolus 

 lunatus seed and in flax seed and tiiat this enzyme is of the emulsin type— e.c. it appears 

 to hydroly.se /i-glucosides — and exhibits similar activities ; but they recognised that it 

 presented certain well-marked differences from emulsin. 



These differences were clearly defined in a later communication, in which they with- 

 drew the statement that ])haHe()lunatiji is decom])Osed by emulsin of almonds, explaining 

 that this liad been made on the basis of " a single experiment in wliich pru.ssic acid was 

 undoubtedly liberated when a connnercial emulsin preparation was addeil to an aqueous 

 solution of the glucoside. Tina experiment has, however, been Repeated frequently, using 

 several different commercial emulsin j)reparations as well as emulsin prepared by our- 

 selves from sweet almonds and in no case have we been able to observe again the 

 formation of pruasic acid within a reasonable time, tliougli in every case prussic acid 



* Dunstan and Henry, 'Roy. Soc. Proc.,' 1903, vol. 72, jip. 285—294 ; Dunstan, Henry 

 and Auld, ihid., B, 190(), vol. 78, pj). H.'i— 1.'')2 ; Dunstan, Henry and Auld, ibid., B, 1907, 

 vol. 79, p|). 315—322. 



t Dunstan and Henry, 15. A. lioport, 19()(;, p. 150. 



