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CHAPTER VI. 



PRUSSIC ACID IN THE LECUMINOS/E. 



Some considerable time before the discovery of prussic 

 acid by Scheele, in 1782, it was known that certain plants 

 possessed extremely violent poisonous properties. The work 

 of Berthelot and Gay-Lussac shed new light on this question 

 and stimulated further research. 



As far back as the beginning of the nineteenth century 

 it was known that several of our colonial peas were of bitter 

 flavour and had a poisonous action. Cossigny, in his 

 " Moyens d'amelioration des Colonies," tells us of a number 

 of accidents that were recorded due to the consumption of 

 certain peas, which, as they grew older, acquired a bitter 

 taste. 



In 1898 the chemist jMarcadieu established, by a 

 series of most interesting experiments, that prussic acid 

 was not actually found in the seeds of Phaseolus hinatus, 

 but was only formed under certain conditions, as, for in- 

 stance, after several hours' maceration. When the seeds 

 are plunged into boiling water the analysis shows no trace 

 of prussic acid, the latter thus being produced in the same 

 circumstances as in bitter almonds. 



M. Boname, Director of the Agronomic Station of 

 Mauritius, was the first to deal with the question. In his 

 report for 1898-99 M. Boname made a thorough study of 

 the occurrence of prussic acid in this plant, and established 

 its presence both in seeds and leaves after they had been 

 macerated in water. 



Like the bitter almond, the d'Achery pea (Phaseolus 

 lunatus) contains a glucoside, amygdalin, discovered by 

 Robiquet and Boutron-Charlard in 1830, which, under the 

 influence of a soluble ferment, emulsin, becoujfis hydrated 



