94 SCIENCE FROM AN EASY CHAIR 



dog. Several cases are on record of the mysterious 

 poisoning produced by this plant in England ; but it is 

 strangely unfamiliar to medical practitioners indeed, 

 practically unknown to them, although I have ascertained 

 that many English people, especially ladies, have been 

 victims for some years to its unsuspected influence. 



At the University of Harvard, in Cambridge, Massa- 

 chusetts, they have made quite recently a thorough 

 examination of the poison-vine in the laboratory, with 

 the following results: The poison is an oil a fixed oil, 

 not a volatile one, as we might have imagined from 

 its mysterious action at a distance. The oil exists in 

 all parts of the plant, even in the fine hairs and cuticle 

 of the leaf. It can be extracted by means of ether, and 

 is one of the most virulent irritants known, having a very 

 curious penetrating and persistent action, and producing 

 violent pain and destruction of tissue when placed on the 

 skin in quantity so minute (one-thousandth of a milligram 

 in two drops of olive oil) as to be beyond the terms of 

 everyday language. It seems to be usually brought to 

 the eyes, nose, lips, and skin of the face and body by the 

 fingers which have touched a leaf or fragments of a leaf 

 in powder. The dead leaf in winter still retains the oil, 

 and minute dust-like particles can carry it. The treat- 

 ment for it is washing with soap, oil, and ether at an 

 early stage of the attack especial care being taken to 

 free the fingers from any minute traces of the oil adhering 

 to them. 



The poison of the poison-vine only acts upon a limited 

 number of individuals, many people being perfectly im- 

 mune. At the same time, the effect upon susceptible 

 people appears to be enhanced with every fresh attack ; 

 even after the total removal of the poison-vine and its 

 dust from proximity to a susceptible person, he or she is 

 apt for some time owing to the retention of some trace 





