June, '12] HOLLISTER: TOBACCO EXTRACTS 267 



be as efficient as the first four preparations and possesses a slight 

 advantage over the sulphate, Xo. VI. Thus it would appear that any 

 advantage gained bj' making a sulphate would be lost bj' its becoming 

 less efficient as an insecticide. 



Experiments with a pure nicotine product and one containing more 

 or less of the tobacco extract show that the pure nicotine solution has 

 several advantages over the latter preparation. The pure solution 

 is much cleaner to handle, less distasteful to use and will not stain 

 clothing or anything with which it may come in contact. Delicate 

 flowers may be sprayed with such a preparation with no discoloration 

 of the petals. 



The manner in which nicotine kills an insect is not known. G. Del 

 Guercio of the Experiment Station at Florence, Italy, believes that 

 the solution of nicotine acts poisonousl}^ upon insects by means of 

 vapors and that these vapors, even in minute quantities, cause irrita- 

 tion, convulsive movements and, if sufficiently increased, death to the 

 insect. It is evident from spraying experiments that nicotine very 

 quickly causes death to those insects having soft and delicate bodies 

 while the harder stronger insects show no detrimental effects. Know- 

 ing the burning sensation which a small amount of nicotine solution 

 will cause when taken into the mouth, it is easy to imagine the effect 

 upon the soft-bodied insect. 



Summary 



1. It may be safely stated that the use of tobacco, one of the oldest 

 insecticides, is becoming more popular as a destroj'er of insects, con- 

 trary to the fate of a large number of the insecticides of earlj^ origin. 



2. A solution of pure nicotine is practically as efficient as the prod- 

 ucts containing a quantity of extractive matter. 



3. Nicotine sulphate possesses no advantage over the uncombined 

 product. 



4. A solution of pure nicotine possesses the additional advantage of 

 being free from the other constituents of tobacco which are nauseous 

 and injurious. 



[This completes the Proceedings. — Ed.] 



ERRATA 



Inadvertenth" the numerals 17 and 18 were omitted in numbering the plates in 

 volume 4 — the sequence jumping from 16 to 19. The references to plate 17 on pages 

 427 and 429 relate to the plate numbered 19. ' , 



