260 SIR RUBERT BOYCE — THE PREVALENCE, DISTRIBUTION AND 



E.vperiment lY. 

 Half Mil ounce of oil poured on to the surface of water in the tub, and 

 larvae placed in the water at 1.40 p.m. in bright sunshine ; at 3.15 p.m. 

 the larvse were yqyj sluggish but still alive ; the petroleum had evaporated 

 from the surface. 



These few experiments show that in bright sunshine the oil film rapidly 

 evaporates, but that the oil which remains in solution still continues to 

 exert a culicide action. Therefore it may be concluded that one ounce of 

 oil to the square superficial yard is sufficient to kill mosquito larvae, but 

 that the watei- should be treated once a week in order to avoid all risk of 

 the survival of larvse. 



Action of Culicides on the Adult Mosquitos. 



In my experience, the l)est, cheapest and most readily procurable culicide 

 is sulphur, whether used in a small way by burning in sulphur pots, or on 

 a large scale by generating it in a Clayton sulphur apparatus. I always 

 recouimend testing the efficac}^ of fumigation by direct experiment, rather 

 than relying upon calculation. For this purpose 1 insert living Stegomyia 

 in a muslin-covered box or in some place where they can be observed from 

 outside the roojii or building. When they are dead I conclude that the 

 fumigation has been successful. The following is a brief statement with 

 regard to the three most generally useful culicides. 



Sulphur. — 2 lbs. to 1,000 cubic feet. The pots containing the sulphur 

 are to be placed in pans containing one inch of water. The sulphur is to 

 be ignited with alcohol, and care must be taken to see that it is well alight. 

 Duration three hours. Brass work and steel goods are liable to injury, they 

 should therefore be removed. 



Fyretlirum poioder. — 3 lbs. to 1,000 cubic feet, applied for three hours ; 

 and it is better that the 3 lbs. be divided amongst three pots than that all 

 the powder be put in one pot. The pots to be placed in pans containing 

 a little water. Pyrethrum powder is used for rooms close to any sick 

 patients, as the fumes which might escape from sulphur fumigation are 

 irritating. This powder is also used in cases whei-e brass work, pianos, 

 telephones, instruments, etc., are present. 



Camphor and Carbolic Acid. — The mixture consists of equal parts camphor 

 and crystallised carbolic acid dissolved l)y gentle heat. It is an exceedingly 

 good fumigalor and does not injure furniture, clothes or brass work ; the 

 odour is pleasant and smells of camphor. A room has a refreshing smell 

 after its use. 



Four ounces are vaporised per 1,000 cubic feet for two hours. The 

 material is placed in an open pan placed over a spirit or petroleum lamp ; 

 white vapour is given off. 



Avoid risk of setting fire to the premises by using care and foresight. 



