440 DISINFECTION 



mentation with a view to obtaining comparable results. First, 

 he recommended the use of a well-known disinfectant giving 

 regular and consistent results, such as pure phenol. Secondly, the 

 source and age of the culture used is of importance. If the 

 culture be in broth, Walker suggests the following procedure: 

 to 5 c.c. of a twenty-four hours' blood-heat culture of the 

 organism add 5 c.c. of the dilute disinfectant. Shake and take 

 sub-cultures at definite intervals in suitable media. Incubate 

 for at least two days at 37 C. If an agar culture be preferred, 

 take up part of the growth on the point of a platinum needle, and dis- 

 tribute it evenly in sterilised water. The resulting emulsion may be 

 used in place of the broth culture. Thirdly, Walker emphasises the 

 importance of working with the same organism for comparable results.* 

 A substance, to be a satisfactory disinfectant, should, according 

 to Andrewes, possess five characters: (a) it should be germicidal 

 within a reasonable time-limit; (&) it should not possess chemical 

 properties which unfit it for ordinary use ; (c) it should be soluble in 

 water, or capable of giving rise to soluble products in contact with 

 the material to be disinfected; (d) it should not produce injurious 

 effects on the human tissues ; and (e) it should not be too costly in 

 proportion to its germicidal value.f 



Mineral acids (nitric, hydrochloric, sulphuric), especially concen- 

 trated, are all germicides, but owing to their corrosive action their 

 application is limited. 



A number of bodies, such as chloroform and iodoform, have been 

 much advocated as antiseptics. The cost of the former and odour of 

 the latter have, however, greatly militated against their general 

 adoption. 



Chloride of lime is a powerful disinfectant. Professor Sheridan 

 Dele'pine and Dr Arthur Eansome have demonstrated its germicidal 

 effect as a solution (1 per cent.) applied directly to the walls of rooms 

 inhabited by tuberculous patients. J Coates confirmed these results 

 in houses in Manchester infected by consumptives. Chlorinated 

 lime ought to be used which will yield not less than 33 per cent, of 

 available chlorine. It may also be used in solid form for decompos- 

 ing matter, excreta, etc. 



Mercuric chloride (corrosive sublimate) has been an accepted 

 germicide for some time. But the experiments of Behring, 

 Crookshank, and others, have proved that the weaker solutions 

 (1-4000) cannot be relied upon. This is, in part, due to the fact that 



* Practitioner, 1902, Ixix., p. 523. 



t Many useful hints and suggestions as to testing disinfectants, and on the whole 

 process of disinfection will be found in Lessons in Disinfection and Sterilisation, by 

 F. W. Andrewes, M.D., F.R.C.P., 1903, p. 81 et seq. ; see also Brit. Med. Jour., 

 1904, ii., p. 13. 



Brit. Med. Jour., 1895, vol. i., p. 353. 



