530 



THE STINGING PROPERTY OF THE GIANT NETTLE 

 TREE (LA PORTE A GIG AS Wedd.). 



By James M. Petrie, D.Sc., F.I.C. 



(From the Physiological Laboratory of the University of Sydney). 



The Giant Nettle-Tree is native to Australia, and grows 

 plentifully in certain of the coastal districts. It is often 

 found attaining a height of over 100 feet, with green, 

 succulent stem and branches, which are very easily broken. Its 

 leaves, often a foot in diameter, are very juicy, and are covered with 

 numerous strong hairs or bristles which are filled with a powerful 

 stinging fluid. If the leaves be lightly touched with the hand 

 these bristles penetrate and break in the skin, causing pain 

 which, however slight at first gradually increases in severity 

 and sometimes lasts for many days. There are instances where 

 children have been ill for weeks with the pain of the sting, and 

 in certain seasons at least, it truly earns its popular name of the 

 " Mad " Tree. 



The poisonous properties of the sap of the leaves form the 

 main subject of this research. From Clifton, 35 miles south of 

 Sydney, a large supply of leaves was obtained. They are soft 

 and succulent when fresh, but exposure to the sun for a day 

 makes them quite dry and brittle, and therefore easily powdered 

 in a mortar. 



Reaction of the sap.— When fresh leaves are steeped in water 

 the latter becomes acid, but leaves which have been air-dried 

 yield a perfectly neutral extract. On distilling fresh leaves and 

 air-dried leaves with pure water, the same definite result was 

 obtained, only that, on long-continued boiling, the neutral dis- 

 tillate gradually became acid, a fact which points to dissociation 

 and liberation of a volatile acid. When the dried leaves are 



