59 



(2) To kill the larvae, among numerous substances experimented with, there will 

 have, 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) Organic: powders of the 

 unexpanded flowers of chrysanthemum, tobacco, j^etroleum and oils, formalin, 

 creso-, certain aniline colors (gallot, green malachite), coal tar. Taking into account, 

 however, the dose necessary to kill the larvte, 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 jiersons. 



(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 nmch 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 larvae 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 for a 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 alread}^ referred to as the yellow aniline dye which they call 

 '• Larycith III." This color has the property of other aniline colors in 

 that it is soluble and difl:usible 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 destro}^ 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 III" will prove to be and Avhether 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. Koss, in his article in Nature of March 29, previously referred 



