DESTKUCTION OF LARV^. 79 



the results were good where the work was properly done. Shortly 

 after operations were begun there was a flight into the city of A'edes 

 soUicitans from the salt marshes northeast of New Orleans. Indig- 

 nant citizens, ascertaining from experts the name and habits of the 

 species, jumped to the conclusion that salting the ditches had brought 

 about suitable breeding conditions for soUicitans and that the invasion 

 of the city by that species was a direct result of the work of the sani- 

 tary officials. Charging mosquito pools with electricity does not 

 seem to have been tried. Mr. Aaron Aaronsohn, director of the 

 Jewish agricultural experiment station at Haifa, Palestine, tells the 

 writer that Professor Blasius, of Berlin, reading a newspaper account 

 that some electrical workers engaged in the vicinity of a river used the 

 electrical current to catch fish, began, some little time ago, to study 

 the effect of electricity on fish, and that he found that by discharging 

 a current into the water he could stun the fish, but did not kill them. 

 Mr. Aaronsohn suggests that this plan may perhaps be tried to advan- 

 tage in certain favorably situated localities to ascertain whether it 

 can be practically used against mosquito larvae. 



In the course of the experimental work with larvicides carried on at 

 the Isthmus of Panama Colonel Gorgas and his assistants have con- 

 structed a larvicide plant at Ancon, and in the August, 1909, Report 

 of the Department of Sanitation of the Isthmian Canal Commission 

 it is stated that 14,600 gallons of larvicide were made at a cost of 

 $0.1416 per gallon. The following is quoted from this report: 



The method of making same is as follows : 150 gallons of carbolic acid is heated in a 

 tank to a temperature of 212° F.; then 150 pounds of powdered or finely broken resin 

 is poured in. The mixture is kept at a temperature of 212° F,, 30 pounds of caustic 

 soda is then added and solution kept at 212° F. until a perfectly dark emulsion, with- 

 out sediment, is obtained. The mixture is thoroughly stirred from the time the resin 

 is used until the end. 



The resultant emulsion makes a very good disinfectant or larvacide. In fact, 1 part 

 of it to 10,000 parts of water will kill Anopheles larvae in less than half an hour, and 1 

 part to 5,000 parts of water will kill Anopheles larvae in from five to ten minutes or 

 less. This property of killing larvae rapidly is of great importance in the Tropics, 

 where continuous rainy periods make crude oil or kerosene much less valuable as a 

 larvicide than it is in northern latitudes having less rainfall. Also, the larvicide 

 acts as an algicide, and thus destroys the food and the hiding places of Anopheles 

 larvae. As it takes up very little room, compared with the area it can be spread over, 

 the cost of distribution will be much less than that of crude oil or kerosene. Consider- 

 ing the large territory which the antimalarial work covers, this item alone is of great 

 financial advantage to the department. 



Tests have recently been made to determine approximately how much of the new 

 larvicide will be needed per month (rainy season) for each district. 



Although this larvicide will be used to a large extent, yet we shall continue to use 

 crude oil for streams having a fair velocity, as such application gives excellent results 

 and is as economical as larvicide would be, as the oil is spread in a very fine film 

 automatically. In order to make the crude oil drip with continuous regularity, a 

 piece of metal similar to that part of a flat-wick lamp which holds the flat wick is 

 fastened to the oil container. It is made somewhat larger than the wick, so that the 



