656 EXPERIMENT STATION RECORD. 



iveuess of these concentrated solutions as compared with Bordeaux mixture; 

 and (4) the insecticides which can be used with these concentrated lime- 

 sulphur solutions. 



It is claimed that the dilutions of the concentrated solutions which may be 

 used with safety and efficiency depend upon the character of the mixture, the 

 foliage to be sprayed, the fungi to be fought, the quantity and thoroughness 

 of the application, and the character of the attendant weather conditions. 

 Taking the above factors into consideration, the following dilutions of commer- 

 cial concentrates testing from 32 to 34° B. are proposed : For apple scab 1 : 30, 

 for peach rot and scab 1 : 200, for peach leaf curl 1 : 15, for grape diseases 1 : 40, 

 for potato blight 1 : 25, and for cherry diseases 1 : 40. 



ECONOMIC ZOOLOGY— ENTOMOLOGY. 



Report of the Bombay Bacteriological Laboratory for the year 1908, W. G. 

 LisTON {Ui>t. Boiithay Bad. Lab. lOOS. vp. l.'j). — It is stated that the Plague 

 Research Commission has been able to show that the differences in the sea- 

 sonal prevalence of plague in such places as Poona and Belgaum as compared 

 with Bombay and the Punjab can be explained by the differences in the several 

 places of the seasonal prevalence of rat fleas, the number of rat fleas present 

 in any particular place being a dominating factor which makes that place par- 

 ticularly liable to plague at any time. Experiments with Clayton gas as a dis- 

 infectant failed to yield satisfactory results under the conditions generally met 

 with in India. This was mainly because the structure of the average Indian 

 house is such that it freely allowed the escape of the gas from innumerable 

 apertures, especially in the roof which could in no practical way be closed. 



Experiments were made with a small type of Leybold's apparatus, especially 

 designed for the destruction of rats in houses. With this machine air is passed 

 over burning coal or coke, preferably the latter, generating carbon monoxid. 

 The gas is then passed through a scrubber and, in the hand machine used in 

 the experiments, is driven to the room to be disinfected along a 14 in. pipe by 

 means of a rotating fan. The gas proved to be very effective in killing rats at 

 low levels in the rooms and even penetrated into burrows which passed in a 

 downward direction beneath the ground level killing the rats contained in the 

 burrows. It failed, however, to kill rats suspended a few feet above the ground. 

 The rats had to be exposed for several hours to the gas before they were 

 killed. Apparently they were not aware from which direction the poisonous 

 gas came, because they did not attempt to escape from the room when liberated 

 in it as they did when Clayton gas was used. Despite the effect on rats, rat 

 fleas escaped unharmed. It was shown that fleas could be exposed for 1* hours 

 without harm in a sample of the gas which contained 6.6 per cent carbon 

 monoxid, while a small rat was killed in 10 minutes. 



Of 110,512 rats examined during the year 13,489 were found infected with 

 plague. Experiments made with insecticides, rat traps, etc., are briefly noted. 



Rat destruction in the Punjab (Jour. Trap. Med. and Hyg. [London], L3 

 {1910), No. 2, pp. 26, 27).— This article includes a quotation from the Sanitary 

 Report of the Punjab for 1908, by S. B. Smith, which relates to the progress 

 of rat destruction in the province. 



'• Rat destruction by trapping is now systematically carried out in over 100 

 municipal towns and in 6.20 endemic centers, or places which, in the past, have 

 been dangerous diffusion centers of plague. . . . Rat poisoning has been 

 limited to those places infected late in the spring, to prevent or delay recrudes- 

 cence, and to healthy villages near an infected one, to render them immune, 

 while the epidemic is going on, The results appear to be favorable, and plague 



