INSTITUTE, PUSA, FOR 1919-20 



ior 



(15) Vermijelli (official) ... 1 



(16) Carbolic acid (3), soft soap (1) Can hardly be tested 



as it removes the 

 epidermis. 



' (ii) Similar tests were made with about 140 other 

 substances from which it appears that it is hardly possible 

 to produce a preparation which will remain fully effective 

 for 3 hours. 



" A brief list of some of those substances which remain 

 effective for over 9 minutes is given below : — 



(1) Cinnamic aldehyde (13), castor oil (100) . . 100 



(2) Creosote (1), Kerosine (19) . . . . 60 



(3) Creosote (5), Castor oil (100) .... 50 



(4) Cresol (5), Castor oil (100) 55 



(5) Carbolic acid (5), Castor oil (100) ... 40 



(6) Iodoform (5), Methylated spirit (100) . . 45 



(7) Thymol (5), Methylated spirit (100) . . 25 



(8) Mustard oil 25 



(9) Alcoholic extract of bed bugs . . . 15 



(10) Proposote (creosote, phenyl propionate) . . 36 



(11) Safrol (50), Castor oil (100) .... 30 



(12) Vinegar . . . . . . . . ' 20 



(13) Napsal (10), Castor oil (100) .... 20 



(14) Alcoholic ext. of Butch 10 



(15) Orthonitrotoluol (10), Castor oil (100) . . 10 



(16) Tar oil (5), Castor oil (100) .... 10 



" (Hi) Tests of repellent power at a distance of 3-4 

 inches. About 40 substances were tested by a comparative 

 method. These led to the conclusion that (1) the factors 

 concerned with distance repulsion and contact repulsion 

 are probably not identical; (2) neither distance repulsion 

 nor contact repulsion is apparently proportional to the 

 poisonous effect on the mosquito of the vapour of the 

 substance used ; (3) mosquitos probably cannot be kept at a 

 distance from the body (by any practically applicable 

 chemical repellent) for any length of time. The following 

 is the list of some of the chemicals tried. They are in order 

 of their merits in each of the three series : — 



(1) (i) Creosote, Napthaline, (ii) Wood oil, (Hi) Oil of 

 Cassia, (iv) Eucalyptus oil, (v) Lavender oil,. 



