82 PASTORAL AND AGRICULTURAL BOTANY 



Western Species (Pacific Coast) 



Leaves trifoliate to 5-foliate Rhus diversiloba. Rhus Metopium, 

 poison wood or doctor-gum of the south is a tree with poisonous juices. 



Susceptibility. As hundreds of persons are poisoned every year by 

 coming into contact with these plants, it is important to discover the causa- 

 tive principle. Immunity from the attack of the poison of these species 

 is relative. Some persons usually those with a blonde complexion are 

 very susceptible. Others are less so, while a large number of persons 

 usually with dark, or swarthy complexions (brunette type) are practically 

 immune. 



Active Principle. Experiments (1897) of Dr. Franz Pfaff of Harvard 

 University Medical School have shown that the poison is a fixed oil, 

 toxicodendrol, closely allied to cardol from the cashew-nut, Anacar- 

 dium occidentalis. It is soluble in alcohol, ether, benzene, and chloroform. 

 It produces an insoluble compound with lead. It is found in all parts of 

 the plants described above. It is insoluble in water and therefore cannot 

 be washed off the skin with water alone. 



The active principle is poisonous to the skin causing inflammation and 

 pustular eruptions known as dermatitis. Small watery vesicles appear 

 on the skin of the hands usually on the soft skin between the fingers. These 

 vesicles may be scattered in mild cases, as they may be very numerous. 

 Usually the eruptions are accompanied by inflammation and itchiness, 

 and the tendency is to scratch the inflamed areas. In severe cases the 

 pustules cover extensive areas with a swollen condition of the parts and 

 redness. Occasionally, if the skin about the eyes is poisoned, the eyelids 

 swell so that the eyes are entirely closed. Later the vesicles are ruptured 

 and their fluid contents are discharged upon the surface forming moist, 

 excoriated surfaces covered in part with crusts. Where the inflammation 

 reaches the mucous membranes of the internal organs by way of the ex- 

 cretory passages the consequences may be very serious. Death has been 

 the result of ivy poisoning in relatively a few cases. 



Remedies. The most efficient remedy that has been found' is a vigor- 

 ous washing and scrubbing of the skin of the affected parts with soap and 

 water using a brush for the purpose. This washes off the poisonous oil 

 before it has a chance to act upon the skin. The oil may also be removed by 

 washing with alcohol, but the washing must be thorough in order not to 

 spread the infection. Such simple remedies as washing the skin with hot 

 salt water, rubbing the juices of rib grass (Plantago lanceolata) the leaves 



