l6 QtJATERCENTENARY STUDIES IN l»ATllOLOGY 



to 50 minutes, B. coli in from 30 to 40 minutes, B. anthracis and Vibrio 

 cholerai in less than 15 minutes; while solutions, varying in strength 

 from I in 5,000 to i in 20,000, were sufficient to inhibit the growth 

 of most organisms. Tr^trop considered a 2 per cent, solution of 

 formaline to be a most efficient antiseptic, and stated that he obtained 

 positive results with it after other preparations had failed. Bird speaks 

 highly of formaline as a disinfectant and antiseptic, but finds that 

 the vapour is more powerful as a disinfectant than the solution. 

 Schepilewsky confirmed the experiments of Bird. Kenwood suggests 

 the use of a 2*5 per cent, solution for spraying. Leslie Mackenzie 

 and Alexander speak of the efficacy of a -5 per cent, solution for 

 general disinfecting purposes. Park and Guerard find that a 3 per cent, 

 solution will kill Anthrax spores in 15 minutes, while a i per cent, 

 solution will kill all other germs in one hour, and most germs within 

 30 minutes. 



Hill and Abram, in their experiments on the disinfection of excreta, 

 found that faeces when mixed with a i in 20 solution of formaline, 

 remained sterile on subsequent inoculation. Houston found that formaline 

 in a dilution of i in 100 did not prevent the growth of B. coli after one 

 hour's contact, while in a dilution of i in 20 it killed that organism. 

 Thresh and Sowden have made a series of experiments to ascertain the 

 strength of solution necessary to ensure sterilisation. Cultures of B. 

 diphtheriae, B. typhosus, B. pyocyaneus, V. cholerae, M. prodigiosus, 

 and Staph, pyogenes aureus were spread on wood, on white-washed 

 surfaces, and on wall paper. The infected surfaces were sprayed with 

 solutions of formaline varying in strength from '5 to 2 per cent. After 

 three to four hours' exposure, the sterility of the sprayed surfaces was 

 tested by means of sub-cultivations, with the following results : — 

 The '5 solution killed all the organisms on wood and wall paper, but 

 failed to destroy the B. pyocyaneus on white-washed surfaces. The 

 I per cent, solution gave similar reactions, but the 2 per cent solution 

 sterilised all surfaces. 



Muir and Ritchie found that to disinfect an organic mixture 

 containing pyogenic organisms, a 10 per cent, solution, acting for 

 half-an-hour, is necessary, and that in the case of pure cultures, a 

 5 per cent, solution would kill the V. choleras in 3 minutes, B. 

 anthracis in 15 minutes, and anthrax spores in 5 hours. When such 



(252) 



