An Experimental Study of Poison Oak. 61 



of ergot into cocks cannot be considered a quantitative method for 

 testing ergot. Oncometric studies of the cock's comb during acute 

 ergot poisoning are now being made. 



44 (740) 



An experimental study of poison oak. 



By Edward von Adelung. 



[From the Hearst Laboratory of Pathology and Bacteriology, 

 University of California.] 



Experiments show that the toxic principle of Rhus diversiloba 

 while not volatile can poison at a distance by means of mechanical 

 carriers. It is not destroyed by subjection for one hour to ioo° C. 

 and is carried, potent, by the smoke from burning Rhus plants. 

 The dermatitis produced by this' plant is a purely local affection 

 and is not spread by the blood or lymph or by the serum of the 

 blebs. The reaction of the sweat has no relation to individual 

 susceptibility. 



Absolute immunity in man has been claimed but was not 

 found to exist, on repeated attempts, in any of the individuals 

 tried (6 persons). In spite of the work of Ford, the conclusion is 

 arrived at that experimental immunity in animals to Rhus toxin 

 has not been proved. The author, working with pure toxin 

 (glucoside) produced by the method of Syme, was unable to 

 intoxicate animals with any reasonable amount. Ford's work 

 was done with a commercial fluid extract containing various 

 impurities. A permanent aqueous suspension of the alcoholic 

 solution of the pure toxin can be prepared, and remains toxic for 

 the human skin. As much as 0.025 gm. of this preparation of 

 toxin can be given intravenously to a 2,000-gram rabbit without 

 fatal effect, and as much as 0.03875 gm. can be given to a 280-gm. 

 guinea pig subcutaneously without fatal effect. Pure alcoholic 

 extract when given subcutaneously produces severe necrosis and 

 death owing to the alcohol itself used as a menstruum, but with no 

 lesions attributable to the toxin. No skin lesions were produced 

 in monkeys, rabbits, or guinea pigs as a rule, but a slight dermatitis 

 was produced on the rabbit's ear at times. 



