was proved to my entire satisfaction "by the copious eruption 

 and formation of numerous vesicles on the back of my hand, 

 on the fingers, wrists, and bare arms while I was distilling 

 €md operating with it, Ceveral persons coming into the 

 room while I was engaged in with it were more or less poison- 

 ed "by the vapours difl\ised in the room; and I even trans- 

 ferred the poisonous effects to some persons, merely by 

 shaking hands with them. 



"The dilute acid, as obtained by me, and stronger solu- 

 tions of its salts, were applied to several persons, and 

 eruptions were produced in several instances, probably by 

 by the former, though not always, which was most likely 

 owing to the dilute state of the acid. Whenever this was 

 boiled, I always felt the same itching sensation in the face, 

 and on the bare arms, which I experience on continual expo- 

 sure of my hands to the juice of the plant." 



PFAFF»S WOBK. 



By far the most valuable work on Rhus toxicodendron 

 is that of Pfaff, From a clinical study of Rhus poisoning, 

 Pfaff came to the conclusion that the poison must be a non- 

 volatile skin irritant. The more volatile the irritant, 

 the q_uicker is its action on the skin. Formic acid acts 

 very quickly; acetio acid, less volatile than formic, acts 

 more slowly, but still much more quickly than poison ivy, 

 the latent period of which is usually from two to five days, 



Pfaff thought that the volatile acid obtained by Maisoh 



-14- 



