SUMAC FAMILY. 135 



are not susceptible and can handle the plant without 

 harm. It is believed by many that those on whom the 

 poison is effective may even be poisoned without handling 

 it, from hairs and pollen grains or even from the smoke 

 of its burning. McNair's recent investigations of Rhus 

 diversiloba Torr. and Gray, which is so nearly like Rhus 

 Toxicodendron that many botanists consider the two iden- 

 tical, have led him to the conclusion that this belief is er- 

 roneous. He finds that the poison is contained in ducts 

 in the bast or inner bark of the plant and that the wood, 

 pollen, hairs, and the corky layers of the bark are harm- 

 less. It is probably the fact that the poison is a non- 

 volatile oil that has led to so much of the popular con- 

 fusion with regard to its dissemination. By unwitting 

 trampling among the plants the poison is deposited on 

 boots or clothing, whence it would become a centre of 

 future distribution. 



The oil has no effect on the skin of the most of the 

 lower animals, and it is stated that almost all domes- 

 ticated animals can eat it with impunity. Dogs, however, 

 are poisoned by it. 



Treatment* consists in the removal of the poison from 

 the skin by solution or by decomposing it chemically. 

 Scrubbing with soap and water is recommended and pro- 

 duces good results. It should be done before the poison 

 has had time to sink deeply into the skin. Alcohol will 

 dissolve the oil, and washing with a 50% solution is effec- 

 tive. It is stated that lead acetate neutralizes the irritat- 

 ing substance. A saturated solution of this salt in 50% 

 alcohol has been proved most effective. 



* In a publication received since going to press, Giissow reports 

 uniformly good results from applications of tincture of iodine, each fol- 

 lowed after twenty-four hours by washing with soap and water (Can. Field 

 Nat., vol. XXXV No. 6). 



