722 Phaseolus Lunatus Beans. [march, 



THE POISONOUS PROPERTIES OF THE BEANS OF 

 PHASEOLUS LUNATUS. 



Professor Wyndham R. Dunstan, F.R.S., LL.D„, and 

 T. A. Henry, D.Sc. 



In 1 901 the Imperial Institute received for investigation 

 from the Director of the Station Agronomique, Mauritius, the 

 beans of Phaseolus lunatus, a plant grown in that Island for 

 use as a green manure, the dark coloured beans of which had 

 proved to be poisonous. It was found on investigation that 

 these beans were capable of yielding considerable quantities 

 of prussic acid, the origin of which was traced to the presence 

 of a glucoside, to which the name phaseolunatin was given, 

 and a ferment, which was able to decompose the glucoside 

 with the formation of prussic acid. 



A full account of this glucoside is given in a paper 

 communicated by us to the Royal Society (Proceedings 

 of the Royal Soc., 1903, LXXII, 285). While this work 

 was in progress, samples of beans known commercially as 

 Paigya, Rangoon, or Burma beans, which were then being 

 imported into this country in large quantities, were sent to 

 the Imperial Institute for an opinion as to their suitability 

 as feeding stuffs by various firms to whom consignments had 

 been offered. Two varieties of these beans occur in commerce — 

 the one pink, with small purple splotches, and distinguished 

 as " red beans," the other pale cream in colour and known as 

 " white beans." Numerous samples of the red beans were 

 received, and each of these on examination was found to yield 

 minute quantities of prussic acid. Only one sample of the 

 white beans was received at this time, and from that no prussic 

 acid could be obtained. 



The red and white Rangoon beans, though as a rule lighter 

 coloured, smaller and less shrivelled than the Mauritius beans, 

 exhibited certain resemblances, which indicated that they 

 also were derived from Phaseolus lunatus. Such marked 

 differences in colour as were shown by the three varieties are 

 well known to occur in species of this genus, and from informa- 

 tion subsequently received from India there appears to be no 

 doubt that these Rangoon, Burma or Paigya beans are produced 

 by Phaseolus lunatus, the beans of which haye long been known 



