DETERMINATION OF GERMICIDAL POWER 643 



patient and the hands of the operator having been disinfected as 

 far as possible, no antiseptic should be permitted to come into 

 contact with the wound, which may be irrigated with warm sterile 

 physiological salt solution. A dry wound is an important element to 

 success, and a dry, sterile, unirritating dressing should be employed. 

 Instruments, sponges, etc., may be kept in sterile salt solution after 

 the preliminary disinfection by heat (not sponges) or chemicals. 

 But the aseptic system requires more care to ensure success than 

 the antiseptic one, and unless the assistants can be Crusted and 

 the details rigorously carried out, the latter seems preferable. 



The Determination of the Germicidal Power 



For determining germicidal power on sporing organisms anthrax 

 spores are generally used, on non-sporing organisms cultures of 

 the B. typhosus are usually employed. 



(1) Thread method. Sterilised silk threads are impregnated with 

 sporing and non-sporing organisms, lightly dried, and then exposed 

 to the action of the antiseptic solution of a known strength for a 

 given time. After treatment the threads are thoroughly washed 

 with distilled water to remove the antiseptic, and sown on the 

 surface of agar or other suitable culture medium. If no growth 

 occurs the organisms are assumed to have been destroyed. As a 

 matter of fact, however, it is extremely difficult to get rid of the 

 last traces of the antiseptic, which may inhibit growth although the 

 organisms may yet be alive, a fallacy which caused an exaggerated 

 value to be assigned to many substances for example, corrosive 

 sublimate. The thread method may still be employed, but after 

 treatment the threads should be sown in broth, or, better still, if 

 pathogenic organisms be the subject of experiment, inoculated into 

 a susceptible animal. The writer finds that in disinfection experi- 

 ments with anthrax spores, surface agar is a much better medium 

 than broth. 



In experiments with corrosive sublimate, by whatever method, the 

 last traces of this substance must be converted into the inert sulphide 

 by treatment with hydrogen or ammonium sulphide. 



(2) Garnet method. Small garnets the size of a pea are sterilised, 

 soaked in a suspension or a broth culture of the organism, removed 

 and dried. The garnets with the organisms attached are then 

 soaked in solutions of the disinfectant of known strengths for 

 various periods of time ; they are then removed from the solution 

 well washed with sterile water, and finally placed in tubes of broth. 



