59 



especially in the flowering period, and, as that extends from April to Oc- 

 tober, it is probably to be avoided at all times. Apart from the results 

 of these experiments I have records of twenty-three cases of poisoning 

 unmistakably chargeable to this form. In my opinion many cases of poi- 

 soning attributed to Rhus are to be referred to this species. 



Of the Sumach, the poison ivy (Rhus radicans L.) Is perhaps the most 

 familiar, although the poison elder (Rhus Vernix L.) is by far the more 

 poisonous. According to Robert Hessler, M. D.,^ "Many persons proof 

 against the common poison ivy readily succumb to this species." Fortu- 

 nately the restricted range of the species, it being confined to the swamp 

 regions of the northern part of the state, its favorite location being tam- 

 arack swamps, prevents it from being as df.ngerous as its virulence would 

 indicate. The poison ivy, however, because of its almost universal dis- 

 tribution through the state is perhaps the most dangerous of the plants 

 in the list. In the experiments, seventeen out of twenty-two poisoned 

 by merely handling the plant. The remaining five responded vigoriously 

 to the rubbing process. The character of the inflammation is too well 

 known to need description in this connection. One of the subjects, a 

 young man of about twenty-two, who was poisoned as the result of 

 "rubbing," allowed himself to go without treatment for three weeks, In 

 order that he might determine whether or not he would in the future be 

 more susceptible to ivy-poisoning. His case of poisoning was quite 

 severe, involving the whole arm and spreading to the neck, being perhaps 

 more serious than ordinary cases. He wrote me last summer that he had 

 not since the experiment escaped with less than two or three poison 

 attacks a year. I have heard from two others that they also have poi- 

 soned since that time by the slightest contact with poison ivy. On the 

 other hand, the other two members of the group of five do not seem to 

 poison any more readily than before the experiment. In the poison ivy, 

 also, the poisonous principle seems most active during the flowering sea- 

 son. The statement that Rhus poisoning occurs from the handling of 

 dried herbarium specimens has not proven true in my experience. De- 

 terminative material placed in the hands of class after class, has never 

 caused a single case of poisoning. It is fair to conclude that two out of 

 three persons will be more or less affected by simply handling poison ivy, 

 and perhaps nine out of ten if the plant is handled at all roughly. No 

 other one of our indigenous plants is so generally poisonous. 



»Proc. Ind. Acad. Sci.. 1896, p. 21. 



