232 PRUSSIC ACID IN THE LEGUMINOS^ 



and gives rise to benzoic aldehyde, or essence of bitter 

 almonds, to glucose and to prussic acid. This glucoside also 

 becomes hydrated under the influence of weak acids. 



In order to bring about this reaction it is sufficient to 

 pound up the almonds and to moisten them ; the contents 

 of the cells react on each other and produce prussic acid, 

 whilst in the whole seeds these two elements remain isolated 

 and inactive. When heated to boiling point the emulsin 

 loses its properties. 



M. Boname has shown that the d'Acherv pea behaves 

 in exactly the same way. Pounded up and distilled im- 

 mediately afterwards, without previous maceration, no trace 

 of prussic acid is found; when macerated for six hours in 

 water this acid is formed and is found in the subsequent 

 distillation. A negative result is obtained if boiling is 

 carried out before maceration. 



Thus, under normal conditions, the d'Achery pea con- 

 tains no prussic acid, and it is only after maceration in 

 water that this acid is formed ; lukewarm water accelerates 

 its formation. It has also been shown that the ripe seeds 

 contain a larger amount and that other varieties of the 

 d'Achery pea are absolutely devoid of glucoside. 



After M. Boname had published his work he was asked 

 by Professor Dunstan to forward some seeds of the d'Achery 

 pea to enable him to investigate the composition of the 

 glucoside which gives rise to the prussic acid. 



Professor Dunstan calls it phaseolunatin, and proves 

 that this glucoside is of different composition to that of 

 amygdalin,, lotusin, &c. He thinks that the ferment which 

 converts this glucoside into prussic acid is in all probability 

 emulsin. 



Since then Dr. Melchior Treub, of Buitenzorg, has made 

 a very complete study of plants containing prussic acid and 

 of Phaseolus lunatus in particular. 



His investigations have been particularly directed towards 

 the leaves in their various states of growth, and he comes 

 to the conclusion that the proportion of prussic acid is very 



