Brenchley . — Organic Plant Poisons . /. 449 
glucoside to be recognized (1830), but in 1906 Greshoff 1 tabulated about 
a dozen cyanogenetic compounds which had been discovered by various 
observers in the Vegetable Kingdom, several being associated with particular 
plants or groups of plants. 
The function of these cyanogenetic compounds in the metabolism 
of the plant is very obscure, and investigators express considerable dis- 
agreement on the matter. Latham (1886) 2 indicated a possible relationship 
between certain cyanogenetic compounds and various albuminous bodies 
that occur in animal tissues, suggesting that possibly the latter may be 
built up from substances derived from the decomposition of the former. 
Hebert 3 (1898) stated that A. Gautier had put forward the theory that 
hydrocyanic acid forms the basis of the synthesis of the vegetable albu- 
minoids. The theory is that absorbed nitrates are dissociated, partly 
because of their great dilution in the cell sap, and partly because of the 
natural acidity of sap. The free nitric acid reacts with formic aldehyde in 
the green cells, giving rise to HCN, C 0 2 , and H 2 0 . 
2 HNO3 + 5 CH 2 0 = 2 HCN+- 3 .C 0 a + 5 H 2 0 . 
It was suggested, however, that the HCN when formed does not remain as 
such, but is promptly transformed in most cases. 
In 1904 Treub 4 made a very full exposition of the theory that hydro- 
cyanic acid is the starting-point for the production of primary nitrogenous 
bodies in plants. He suggested that in most plants, directly the HCN is 
formed, it enters into such stable compounds that its presence cannot be 
detected. Later on he stated that possibly HCN is the first recognizable 
product of the assimilation of nitrogen and perhaps even the first nitro- 
genous compound that is formed. Treub 5 repudiated the suggestion of the 
protective function of HCN on the grounds that it has neither a nauseous 
smell nor a taste that is repugnant to animals, and that it has even been 
found that some lower members of the Animal Kingdom, such as nematodes, 
arachnids, and others, are definitely encouraged by the presence of hydro- 
cyanic acid in the tissues of the plants on which they feed and live. 
Guignard 6 in dealing with the cyanogenetic glucosides found in 
plants concluded that they functioned as reserve materials, though 
perhaps of an unusual nature. He suggested that while they appeared 
to be nutritive, yet possibly their actual role varies with their constitution. 
In 1906 Dunstan and Henry 7 summed up the march of ideas con- 
cerning the function of hydrocyanic acid in plants thus : 
1 Greshoff, M. : Bull. Sc. Pharm., vol. xiii, 1906, pp. 589-602. 
2 Latham, P. W. : Brit. Med. Journ., vol. i, 1886, pp. 629-36. 
3 Hebert, A. : Ann. Agron., vol. xxiv, 1898, pp. 416-40. 
4 Treub, M. : Ann. Jard. Bot. Buit«, vol. xix, 1904, pp. 86-145 ; vol. xxiii, 1909, pp. 85-118. 
5 Ibid., vol. xxi, 1907, pp. 107-14. 
6 Guignard, L. : C. R., vol. cxli, 1905, pp. 1193-201 ; vol. cxlvii, 1908, pp. 1023-8. 
7 Dunstan, W. and Henry, T. A.: Report Brit. Ass. York, 1906, pp. 145-57. 
