May, 1921] 
MCNAIR — TRANSMISSION OF RHUS POISON 
3. Distillation, either destructive or with ether, when done under reduced 
pressure, gave non-toxic distillates. 
From the results of these distillation experiments it can be safely argued 
that the poison is non-volatile and that if non-volatile it can not be carried 
by entrainment with a volatile substance. It has been considered by some 
as a non- volatile poison carried by a volatile oil. 
In the investigation of the smoke of the burning plant (Von Adelung, 
46), leaves were placed in a glass combustion tube. The glass tube was 
then heated until the leaves began to smoke. The smoke was blown against 
the skin of a susceptible individual. Dermatitis resulted. The experiment 
was repeated with the addition of cotton plugs in each end of the tube. 
Dermatitis did not result. 
It was thought that perhaps condensation of the irritant might have 
occurred on the cotton. The experiment was therefore repeated (McNair, 
30), glass wool plugs being used instead of cotton. The glass wool was kept 
at the same temperature as the burning leaves. No dermatitis resulted. 
It is concluded, therefore, that the non-volatile poison is carried by particles 
of soot in smoke. 
It is also possible to determine the non-volatility of the poison phys- 
iologically. A fresh leaf of poison oak was lightly glued to the concave 
side of a watch glass about six inches in diameter. The watch glass was 
then taped on the breast of a susceptible person (the concave side inward) 
and left there for half an hour. No dermitis resulted. The foregoing 
experiment was repeated, substituting for the leaf a drop of sap. No ill 
effects resulted. 
A drop of sap was now placed on the skin of a susceptible individual, 
and the area was covered by a watch glass. Dermatitis occurred after a 
few hours, but only in the area to which the sap was applied. It did not 
spread. If the poison were volatilized with moderate ease, at ordinary 
temperatures, it would have caused a general irritation at, as well as around, 
the area to which it had been applied. Volatile poisons rapidly penetrate 
into the tissues, and diffuse there with great ease. Such is the case with the 
various oils of turpentine, many ethereal oils from the vegetable kingdom, 
and numerous substances belonging to the aliphatic series, e.g., chloroform 
and ethyl chloride. Petroleum, benzol, and other compounds of the 
aromatic series cause local irritation in essentially the same way (Schmiede- 
berg, 41). 
In another experiment, sap was placed on the skin of a susceptible 
person. After dermatitis had occurred, the affected section of the skin 
was cut out and thin sections were mounted on microscopic slides. These 
sections showed that the poison had penetrated but slowly in the skin 
(McNair). If the poison were volatile, penetration would occur more 
rapidly and diffusion would be greater. 
In ordinary cases of Rhus poisoning, dermatitis is not noticed until 
