480 



Prof. H. E. Armstrong and others. [Nov. 23, 



Unfortunately, we have not yet been successful in our attempts to isolate the 

 glucoside : either the amount present has been too small for us to separate it 

 from the large amount of other substances which are extracted with it or 

 we have been unfortunate in our choice of method. 



The following typical determinations of hydrogen cyanide obtainable from 

 the plant may be quoted as showing that the amount present is but small : — 

 - ■ » 



Source and date (1911). Per cent. HON. 



1 Portrush. May 22 0-055 



: Ballantrae. June 7 0-017 



, Rothamsted (Wild). June 10 | 0-019 



riA. July 24 1 0-049 



Rothamsted (grown on the barley J 2a. „ ! -044 



plots from French seed) | 3a. „ I 0-037 



I 4a. „ 0-030 



Lewisham — Kimmeridge. September 28 (grown at Lewisham in 1911 -048 

 j from seed collected at Kimmeridge in 1910) 



Taking the highest value (0 - 055 per cent.), at most about - 5 per cent, of 

 linamarin can have been contained in the plants examined by us. 

 Unfortunately, in drying the plant, even when this is done very carefully 

 and rapidly at a low temperature, much of the glucoside is destroyed. It 

 will be desirable therefore to work with the undried plant in future. 



To determine the enzymic activity of the plant we usually expose it to the 

 action of toluene and afterwards dry it rapidly, in vacuo, over oil of vitriol. 

 The dried material is then finely ground. To carry out the determination, 

 20 c.c. of an M/5 solution of linamarin (09886 grm.) is digested with 

 2 grm. of the leaf material during 24 hours at 37°. The amount of 

 hydrogen cyanide liberated is then determined in the manner described in 

 No. XIII of our " Studies on Enzyme Action." 



The typical results given on p. 481 may be quoted in illustration. 



From the experience gained during the past year, it is clear that in future 

 it will be necessary, in all cases in which hydrogen cyanide is not detected, 

 to test for enzyme as well, so as to discriminate between plants in which 

 both cyanide and enzyme are present and those in which enzyme is 

 present but no cyanide — and to ascertain whether these latter alone have 

 temporarily lost the power of storing the cyanide. 



