155 



Phosphorus is the most effective rat poison, arsenic coming next. 

 Danger to human Hfe can be obviated by care in distribution. These 

 poisons cause plague-infested rats to die so rapidly that the virus is 

 unable to become -^-idely spread. Phosphorus rat-poison retains its 

 effectiveness for more than twenty days and arsenic rat-poison even 

 longer. Distribution is simple and economical when compared with 

 other preventive measures, and neither commercial nor industrial 

 enterprises are interfered with. The more widely the poison is dis- 

 tributed to every house the better the results ; where the poisons were 

 distributed to several houses in a locality no rat could be found there. 

 It Avas found that the bacteria in the dead body of the rat are naturally 

 destroyed within from two to twelve days when the temperature is 

 low, and the body of the rat decays. 



Creel (R. H.) & Paget (F. M.). Cyanide gas for the destruction of 

 insects,— t/. 5. Public Health Repis., Washington, D.C., xxxi, 

 no. 23, 9th June 1916, pp. 1464-1475. 



A series of practical experiments have been conducted in order to 

 determine the comparative insecticidal values of cyanide gas and 

 sulphur dioxide. During the tests, the outdoor temperature varied 

 from 33° to 70" F., but with no noticeable difference in results. The 

 standards arrived at are provisional, applying to generally existing 

 conditions and not to extraordinary or unusual situations. For 

 instance, while it is believed that cyanide gas in the proportion of 

 2| oz. of potassium cyanide per 1,000 cubic feet, exposure for one hour, 

 mil destroy fleas in the majority of instances, such a strength would 

 hardly kill these insects were they lodged in tightly packed luggage, 

 which would require to be opened and to have its contents spread out. 

 For routine fumigation the following proportions per 1,000 cubic feet 

 of space are recommended. For mosquitos : Potassium cyanide, 

 0-4 oz. for 15 minutes ; sulphur, 2 lb. for one hour. For bedbugs : 

 Potassium cyanide, 5 oz. for one hour. For body lice : Potassium 

 cyanide, 10 oz. for two hours ; sulphur, 4 lb. for six hours. For 

 cockroaches : Potassium cyanide, 10 oz. for one hour ; sulphur, 

 4 lb. for six hours. For fleas : Potassium cyanide, 2| oz. for 15 

 minutes. For fleas and rats a standard of 5 oz. cyanide or 4 lb. sulphur 

 has already been recommended [see this Review, Ser. B, iv, p. 25]. 

 The unit price of c3-anide fumigation in the proportion of 5 oz. cyanide 

 per 1,000 cubic feet was i^d. at the prices then ruling (12|f/. per lb. 

 for potassium cyanide and Id. per lb. for sulphuric acid). The price 

 for sulphur fumigation was 5d. at the strength of 41b. per 1,000 cubic 

 feet. Cyanide fumigation costs only one-ninth of sulphur fumigation 

 in the case of mosquito destruction, apart from occupying much less 

 time. Furthermore the dilution of the cyanide gas after diffusion is 

 such as practically to ehminate all danger to human life. For destroy- 

 ing bedbugs, cockroaches and body hce, sulphur is a cheaper fumigant 

 than cyanide, but the latter possesses obvious advantages. The 

 detailed results of these experiments are given in a series of ten 

 tables. 



