44 



Rhodora [March 



very slowly at ordinary temperatures. A sample of it, which had been 

 kept in an open porcelain dish for over 13 months, was partly converted 

 into resin, but the remaining oil proved to be just as active as before. 

 The active oil was also prepared from plants collected during the 

 winter after having been covered with snow for weeks and from dry 

 stems and branches which had been kept in the laboratory for over a 

 year. 



To test the strength of the " Toxicodendrol " I made many experi- 

 ments and found the oil active in the minutest quantities; in one 

 case as little as 1TJ W m S- of the oil «ii«aolved in 2 drops of olive oil 

 proved effective. 



The time of incubation varied from 18 hours to 9 days. This long 

 period of incubation and the stability of the oil explain the belief, that 

 direct contact is not necessary to contract the disease. When the 

 first symptoms appear, several days have usually passed and a person 

 may then not remember having come in contact with the plant. On 

 the other hand some of the oil may stick to the clothing etc. and 

 this may cause the disease even after several months have elapsed. 

 In making these experiments I handled more than 25 kg. of the plants, 

 and several hundred persons passed through the laboratory, where 

 these experiments were made, but not one of those who did not come 

 in direct contact with the plants or the free oil was poisoned. 



It seems possible that poisoning might be caused by small parti- 

 cles of the plant, such as pollen and the hairs from the leaves, being 

 carried through space by the wind and thus brought in contact with 

 the skin or clothing, for as above stated, the oil is contained in all 

 parts of the plant and even the hairs of the leaves may be seen under 

 the microscope to contain oil. 



Having defined the properties of "Toxicodendrol" we may now 

 outline the rational treatment of ivy poisoning. As we have seen 

 Toxicodendrol is not a volatile oil, but on the contrary is very 

 stable, we must endeavor to remove it as quickly as possible and 

 prevent its spreading. 



This can be done by vigorously washing the affected and exposed 

 parts with soap and water and a scrubbing brush ; that is to say by 

 mechanically removing the oil. As the active principle is very 

 soluble in alcohol and gives with lead acetate a precipitate which is 

 nearly insoluble in alcohol, other processes may be employed to 

 remove the oil. The exposed parts may be washed repeatedly with 



