May, 1921] 
MCNAIR TRANSMISSION OF RHUS POISON 
In 1788 Du Fresnoy, experimenting with R. radicans, steam-distilled 
its flowers and leaves. The distillate was not poisonous, but the residue in 
the still remained toxic. 
Fontana (13) experimented with R. Toxicodendron. Because of his 
marked susceptibility to the poison he was forced to stop before he had 
determined whether or not the poison is volatile. 
Two years later, Van Mons (45) collected about fifteen cubic inches of 
gas given off by a plant of R. radicans. Chemical experiments were carried 
on with this. He then engaged his brother, who was very sensitive to the 
poison, to hold his hand for more than one hour under a glass bell jar con- 
taining gas from the plant obtained in the middle of the day. A month 
later, not having noticed any eczematous symptoms, he repeated the same 
experiment with gas collected under a cylinder covered with black card- 
board. He felt, even during the immersion, a burning sensation, and 
developed a typical case of Rhus dermatitis. Van Mons concluded that 
the poisonous principle of R. radicans is a gaseous hydrocarbon which ema- 
nates from the plant only at night, on cloudy days, or in the shade. 
In 1798, Horsfield, a medical student at the University of Pennsylvania, 
stated that some people were affected by the exhalations of R. Vernix and 
R. radicans to a distance of twenty feet from the plant. He also noticed 
that dermatitis was produced by the immediate application of the juice of 
the plant to the external surface of the skin. In analyzing R. radicans he 
placed two pounds of the flowers and leaves with several quarts of water in a 
small copper still. The distillate was not poisonous, but the residue in the 
still retained its toxicity. 
Lavini (25) considered the poison of R. Toxicodendron a gum resin, 
mixed with a "subtil" acid principle, qualified to combine with the hydro- 
carbon gas which emanates from the plant after sunset. According to him, 
the effect of the sap squeezed from the leaves is analogous, but less intense. 
The effect of "water" distilled from this plant was still less intense. 
Khittel (22) attempted a more thorough chemical analysis of R. Toxico- 
dendron. Because of his inability to find the poison by the processes out- 
lined, he considered it a volatile alkaloid. 
halaisons d'une plante de rAmerique Septentrionale produisent sur le corps humain. 
Mem. de I'Acad. de Berlin 61-80. 1777. Ditto. Journal de Physique 21: 161-175. 
HuNOLD, — . Piepenbrugs Archiv fiir die Pharmac. i : 279. 
Kraus, J. C. Verhandeling over der aard en de werking det geneeswiddelen, welke ter 
bestrijding van zenuwkwalen en derzelver toevallen worden Aangewend. Amsterdam, 
1819. 
Kruger, — . Archiv fur die Pharmac. i: 261. 
Monti, Guiseppe. De plantis venenatis, Accademia della scienze dell' Instituto di 
Bologna. Commentari II, 3: 160-168. 1755. 
PoRNAi, — . Giornale per ssvire alia storia ragionata della medicinia di questo secola. 
Venezia i : 83. 1783. 
WiLLEMET, Remi. Observations sur les efifets du Rhus radicans. Jour, de Phys. 51: 369- 
370. 1800. Ditto. Journ. de Med., Chir., Pharm., etc., Paris i: 209-211. 1801, 
