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(2) To kill the larvee, among numerous substances experimented with, there will 
nave, in decreasing order, culicidal action: (a) Mineral: sulphurous oxide, perman- 
ganate of potash with hydrochloric acid, common salt, potash, ammonia, carburet of 
lime, corrosive sublimate, chloride of lime, the bisulphites, sulphate of iron or cop- 
per, lime, bichromate of potash, and sodium sulphite. (b) Organie: powders of the 
unexpanded flowers of chrysanthemum, tobacco, petroleum and oils, formalin, 
cresol, certain aniline colors (gallot, green malachite), coal tar. Taking into account, 
however, the dose necessary to kill the larvee, the practicability and the price, all of 
the mineral and some of the organic substances are excluded, and there remain as 
available the vegetable powders, petroleum, and the aniline colors. 
(3) To kill aerial mosquitoes, we have odors, fumes, or gases. Among the odors 
are turpentine, iodoform, menthol, nutmeg, camphor, garlic. Among the fumes 
are tobacco, chrysanthemum powder, fresh leaves of eucalyptus, quassia wood, 
pyrethrum powder. Among the gases, sulphuric oxide. It is, however, to be noted 
that for these odors, fumes, or gases to exercise their culicidal action they must fill 
or saturate the whole ambient; otherwise they produce only apparent death, or at 
most only a culicifugal action, which sometimes in houses may be useful in protect- 
ing man from being bitten by mosquitoes, and preventing the latter infecting him 
when they have sucked the blood of malarious persons. 
(4) The problem of the destruction of mosquitoes is experimentally soluble, but 
practically it will only be so when economic interests desire it. In this latter sense 
it is remarkable that the old larvicidal use of petroleum has not become much diffused 
in those places where it is very cheap. The chrysanthemum plants might be grown 
on a large scale, this making the malarial place itself produce that substance which 
frees it of the mosquitoes that infest it. 
(5) The opportune season for killing the larvee is in the winter, when they are in 
least numbers in the waters and new generations are not born; this also is the season 
for their destruction in houses, for they come here fora warmer abode. Their habits 
and places of nesting should be studied to this end. This may not be accomplished 
on a large scale as easily as some boast; nevertheless, after the treasures spent by 
nations and individuals for preserving vines and vegetation from the oidium, the 
peronospora, and the phylloxera, we may hope that something may be done for 
protecting the life of man from the mosquitoes of malaria. 
It will be noticed that they really exclude from further consideration 
all substances except vegetable powders, petroleum, and the aniline 
colors. By vegetable powders they refer to the powders from the 
flowers of plants of the genus Pyrethrum, and their experiments upon 
the aniline colors practically center upon the recommendation of the 
substance already referred to as the yellow aniline dye which they call 
‘‘Larycith II.” This color has the property of other aniline colors in 
that it is soluble and diffusible in water. The practice recommended 
is to make a concentrated solution, which is poured into the pool or 
pond to be treated. It is said by the authors that it will destroy all 
insect life and fishes, but is harmless to warm-blooded animals; thus 
domestic animals may, without danger, drink from pools being treated. 
Just what ‘‘ Larycith IIL” will prove to be and whether it will be 
available for use in this country unfortunately can not be ascertained 
at the present moment. Correspondence has been entered into with 
large dye firms in New York who have sent abroad for information. 
Dr. Ross, in his article in Nature of March 29, previously referred 
