Oct. 16, 1916 
Effects of Nicotine as an Insecticide 
109 
shows that this substance was widely distributed, and it is also logical 
to think of the nicotine accompanying the stain wherever it went, except 
when the stain penetrated hard tissues, such as chitin. In the higher 
animals nicotine is chiefly excreted through the kidneys, because it is 
found in the urine soon after it has been administered. Since the 
Malpighian tubules take up indigo-carmine so readily, it seems that 
these organs would also readily excrete poisons contained in the blood. 
As indigo-carmine does not seem to pass through the walls of the small 
intestine and those of the rectum, they are either impermeable to this 
substance or the stain has been so changed that it has lost its original 
permeability. The same reasoning might also be used for nicotine or 
any other stomach poison which acts similarly, although according to 
Cushny (6) iron behaves quite differently when administered to the 
higher animals. He says: 
Iron injected into the veins of animals is stored up in the li\er, spleen and bone 
marrow, but is taken up from these organs again, and is excreted by the epithelium of 
the caecum and colon. When iron is given by the mouth, therefore, it may either pass 
along the canal and be thrown out in the faeces, or it may be absorbed, make a stay in 
the liver, be excreted in the large intestine, and again appear in the stools. 
He also states that iron has been followed in its course through the 
tissues by histological methods, but nothing is known about the changes 
which iron preparations undergo in the stomach and intestine, or the form 
in which iron is absorbed. 
3.— TRACING NICOTINE AS A FUMIGANT TO NERVOUS SYSTEM 
While experimenting to determine the physiological effects of nicotine 
as a fumigant, various insects were fumigated with pure nicotine and a 
40 per cent nicotine-sulphate solution. The results indicated that the 
nicotine fumes were condensed wherever they went. Several of the green 
peach aphids (Myzus persicae) that had been killed by the fumes from 
the solution of 40 per cent nicotine sulphate were fixed with the mixture 
consisting of absolute alcohol and phosphomolybdic acid. A careful 
study of the sections made from these aphids gives the following results: 
As already stated, these aphids appeared to be coveted with fine spray 
before they died, indicating that the fumes had changed into tiny drops 
of liquid. In the sections it is easily seen that the entire integument is 
covered with minute particles of precipitate. Plate 3, figure B, taken 
from a molting aphid, well represents the precipitate ( pr ) on the integu¬ 
ments which have been cut obliquely. It is to be noted that the minute 
precipitated particles lie on the outside of both the old (intf) and new 
integuments (inf), and even between them, but never on the inside of the 
new integument. Aphids, not fumigated, put into the same fixative 
occasionally show a little precipitated material on the outside of the 
integuments, but usually it is easily distinguished from the precipitate 
