OEGANIC POISONS AND DEUGS 95 



took place through the importation of the wild Phaseolus 

 from the East under the name of Java or Eangoon beans. 



. As regards the mechanism of poisoning by these materials, 

 it is necessary to emphasise several important points : 



1. In the dried material the enzyme and glucoside are 

 not in contact, and therefore no fermentation with forma- 

 tion of hydrocyanic acid occurs. 



2. After mastication the pulped mass at the body tem- 

 perature is in a most favourable condition for fermentation, 

 and the disengagement of hydrocyanic acid is therefore 

 rapid in the rumen or stomach. 



3. A moist heat of over 60° C. destroys the enzymes, but 

 it must be remembered that their destruction by dry heat 

 requires prolonged heating at at least 100° C, the cyano- 

 genetic glucosides in themselves neither appearing to be 

 particularly poisonous nor to be acted upon by the various 

 digestive ferments.* 



In spite of hot pressing, which would be expected to 

 destroy the enzyme, the great majority of linseed cakes 

 still contain active enzymes. Linseed cake rarely, how- 

 ever, yields more than 0'025 per cent, of hydrocyanic 

 acid, although as high a percentage as 0*056 has been 

 observed. It will therefore be only under exceptional 

 conditions that linseed can prove poisonous, as has been 

 shown by feeding experiments.' 



As regards the preparations likely to be encountered in 

 pharmacy and the arts, the B.P. hydrocyanic acid is a 

 2 per cent, and Scheele's acid is a solution of from 4 to 

 5 per cent., whilst the very volatile and exceedingly 

 poisonous anhydrous acid is never encountered outside 

 the laboratory. 



Potassmm cyanide is the commonest salt, and is also 

 very poisonous. It is a colourless crystalline solid, having 

 a faint smell of prussic acid, and yielding an alkaline 

 solution in water. 



Potassium cyanide appears to be slightly less toxic than 



* In MoCall's experiments (foe. cit.) meal of Java beans appears to 

 have poisoned even after one hour's boiling. 



