128 JOURNAL AND PROCEEDINGS. 



succeeding attacks to fresh exposures to the plant's emanations, 

 without the patient's knowledge. An able advocate of this view 

 thus expresses himself in regard to the poisonous emanation : 

 " Being volatile, it may be readily diffused, and like malaria or the 

 cause of hay-asthma, may act under favorable circumstances, as of 

 aerial currents and susceptibility in the recipient, at a considerable 

 distance from its source. Now it is well known that no protection 

 is conferred by a prior attack, and hence it might reasonably happen, 

 that a person having suffered from ivy poison one season, would 

 also suffer the next by reason of susceptibility, even though 

 scrupulous precautions should be taken to avoid direct exposure. 

 In such a case the diffused emanations might be sufficient as an 

 exciting cause to account for the recurring attack. It is to be noted 

 that the so-called recurring cases always take place during the 

 summer season, and at the period of the plant's poisonous activity, 

 but never in the winter, which lends support to the supposition of 

 the existing cause being diffused in the atmosphere." These 

 plausible arguments do not however, to my mind, clear up all the 

 reported cases of recurrence. A gentlemen was poisoned one year 

 in this country, and the next he went to Europe, where, at the 

 same season of the year as that when he was first poisoned, most 

 of the symptoms returned. Now, being in Europe, he could not 

 be exposed to the noxious emanations of poison ivy, and the oppo- 

 nents of the recurrent theory would have to fall back on the far- 

 fetched argument that he might have been exposed to noxious 

 effects, resembling those of poison ivy, from some poisonous shrub 

 of Europe. Further, in some cases the eruption is said to have 

 returned annually for several years, and one can hardly imagine 

 a person suffering a number of consecutive attacks without noting 

 his fresh exposure in at least some of them. 



In the New York "World" last year there appeared in an arti- 

 cle, by one Edmund Collins, on the poisonous rhuses, the following 

 extraordinary statement : " Every one does not know what is the 

 meaning of the term ' poison-ivy.' They do not know that a little 

 while after touching the leaves or branches of a poisonous tree or 

 ivy, a vivid red rash appears upon the hand, wrist or leg, and then 

 spreads over the whole body, A microscopist removes a little of 

 the rash, puts it on the slide of the microscope, and, under a glass 

 with a magnifying power of 300 diameters, sees an active little para- 



