104 



This is a cresol preparation readily soluble in water, used for disin- 

 fecting purposes b} r the New Brunswick board of health. It forms no 

 surface scum, and turns the water milky when added in any quantity. 

 As it was intended to make a field application to breeding pools within 

 a certain portion of the city limits the substance was tested a little 

 more fully than some others; but as the tests were made in early Juty, 

 when no Anopheles larvae were available, only larvae and pupae of 

 Culex pungens were used. 



The stock solution in this case was 1 to 200, and 6 jars each with full 

 10 ounces of water were used. The larvae in each case ranged from 

 two or three days old to full grown, and between 50 and 100 were in 

 each jar. 



Jars Nos. 1 and 2 each received stock solution to make the mixture 

 1 to 12,800, and at that dilution the water was faintly white tinged. 

 After twenty minutes, 50 per cent of the larvae were dead--mostly the 

 smaller specimens. After two hours, 25 per cent, including all the 

 full-grown examples, were yet alive, and eighteen hours later there 

 had been practically no change, except that some larvae had pupated. 



Jar No. 3 received stock solution to make the mixture 1 to 6,400, 

 and the water was appreciably white-tinged. After twent} T minutes 

 only about 10 per cent of the larvae were alive, and in two hours only 

 pupae and a few full-grown larva 4 remained alive. After eighteen 

 hours a few more larvae were dead, but pupae remained unaffected. 



Jar No. 4 received stock solution to make the mixture 1 to 3,200, 

 which rendered the water a little translucent. Though this jar had 

 double the amount of stock solution put into No. 3, the effect was 

 exactly the same, and at the end of ten hours there were quite as many 

 larvae and all pupae left unaffected. 



Jar No. 5 received stock solution to make the mixture 1 to 1,600, 

 and this made a decidedly milky, opaque liquid, in which all the larvae 

 were dead in five minutes. One pupae survived after three hours, but 

 was so feeble that its death was certain. 



For practical work, mixtures ranging between 1 to 1,000 and 1 to 

 1,500 will prove fatal to larval life— that is, to a body of water con- 

 taining 1,000 gallons or thereabouts, 1 gallon of chloro-napthalum must 

 be added to kill all the mosquito larvae in it. At that strength it is 

 also a good disinfectant, and its use in gutters and on dumps is cleans- 

 ing and the effects are lasting. 



Pools in which mosquitoes bred in the Sixth ward, in New Bruns- 

 wick, were twice treated during the summer with this material and in 

 each case the larvae were killed off and the pools remained free until 

 flooded by heavy rains. The effect on the local mosquito supply was 

 quite marked. The manner of application was to pour a gallon of the 



