June, '12J HOLLISTER: TOBACCO EXTRACTS 265 



To determine this, experiments have been carefully carried out by 

 the writer with different nicotine preparations now on the market. 

 These preparations contained percentages of nicotine which varied 

 from 7 to 40 per cent. They also varied in weight, color and odor. 

 As a check upon these, dilutions of pure nicotine were used, a solution 

 containing 10 per cent nicotine. 



The preparations were guaranteed to contain the following per- 

 centages of nicotine: 



Xo. 1 8 per cent. 



Xo. II 25 per cent. 



Xo. Ill 30 per cent. 



Xo. IV 40 per cent. 



Xo. V (Check) 10 per cent. 



Xo. VI 7 per cent. 



No. VI was nicotine sulphate made from pure nicotine combined 

 with sulphuric acid. 



As a test insect the common bedbug, Cimex lectularius, was used. 

 The bedbug was used not to find a remedy for its extermination, but 

 because it was easy to obtain and because of its resistance and tena- 

 cious hold upon life. A total of over sixteen hundred insects were 

 used in the experiments. 



The method of making the tests conform with that described in a 

 paper on "A Contribution to Our Knowledge of Insecticides" which 

 was read before the International Congress of Zoologists at Boston in 

 1907. The insects were placed in glass tubes covered at the ends with 

 cheese cloth, a thin cloth being used to allow the free passage of the 

 liquid. With a hook fastened into the cloth the tube was quickly 

 plunged into the solution. By rapid agitation the protective air 

 globules, which surround the spiracles can be removed and the whole 

 of the insect comes in contact with the insecticide. At the end of one 

 minute the tube was withdrawn and the insects quickly removed to a 

 dry paper and covered with a clock glass to prevent any lively ones 

 from escaping. The first results were noted at the end of twenty- 

 four hours. Bugs dipped in clear water for one minute recovered 

 and became as lively as ever in a very short time. This proved that 

 the insects dipped in the nicotine solution did not die from drowning. 



Four chfferent dilutions were made of the products tested, the 

 dilutions containing respectively .50, .75, 1 and 2 per cent of pure 

 nicotine. Five fresh dilutions were made of each, using ten insects to 

 a test and no insect or dilution was used twice. 



The follo"wing results were noted at the end of the first twenty-four 

 hours. 



