- 5 6- 



poisonous and the second non-poisonous. A thin layer of the 

 first was left in an open crystallizing jar for four months when 

 it was found to be still poisonous. 



Another sample of five grams was left in an open vial on a 

 laboratory shelf for ten months, including the hot summer months. 

 This was then tested on my arm and was found to be still active. 

 These facts are sufficient to prove that the poisonous principle 

 is non-volatile. Doubtless the cases of poisoning that have oc- 

 curred from opening retainers have been due to minute particles 

 of the lac being forced out with the vapor. 



The poison is extremely active even in minute quantities and, 

 as it forms a part of the resinous body, it is very difficult to remove 

 from the skin or clothing. Washing with soap and water is not 

 sufficient to insure its removal. If the hands after contact with 

 the lac are thoroughly washed with soap and water until they 

 are to all appearances clean, and then wet with a solution of caus- 

 tic alkali, black spots will appear wherever the lac has been in 

 contact. A mixture of powdered soap, pumice stone and sodium 

 carbonate gives the best result. However, to insure safety 

 I have usually followed this with soap and sand. The poison 

 seems to have little or no effect upon the thick skin on the inside 

 of the hand, but, to prevent its transmission to other parts, it should 

 be removed as soon as possible. For example, by accident some 

 of the benzin solution was thrown into one eye and over one 

 hand. The eye was thoroughly washed with benzin and alcohol, 

 but in my anxiety for the eye, the hand was forgotten for twen- 

 ty or thirty minutes, when it was thoroughly washed with ben- 

 zin and alcohol followed by soap and sand. The eye escaped 

 without further inconvenience than that caused by the benzin, 

 but in thirty-six hours the surface of the hand became slightly 

 swollen, itched considerably for a week and then appeared to 

 be covered with a thin dry scale, which finally disappeared. Since 

 then I have tested different parts of the substance to determine 

 whether or not they were poisonous, by cutting a hole 6 mm. in 

 diameter in a piece of gum paper, pasting this on the arm and 

 applying the substance to the opening. In from thirty minutes 

 to one hour the paper was removed and the spot washed with 

 ether or benzin. When the substance was poisonous the spot 

 became red and began to itch within 30 hours. From three to 

 five vescicles usually appeared. The itching was not intense, 



