THE EFFECTS OF CERTAIN ANTISEPTICS 173 



of the sulphurous acid gas. The practical applications of this 

 agent are therefore limited. 



Potassium Permanganate. The action of this agent very 

 much depends on whether it can obtain free access to the 

 bacteria to be killed or whether these are present in a solution 

 containing much organic matter. In the latter case the oxidation 

 of the organic material throws so much of the salt out of action 

 that there may be little left to attack the organisms. Koch 

 found that to kill anthrax spores a 5 per cent, solution required 

 to act for about a day ; for most organisms a similar solution 

 acting for shorter periods has been found sufficient, and in the 

 cases of the pyogenic cocci a 1 per cent, solution will kill in ten 

 minutes. There is little doubt that such weaker solutions are of 

 value in disinfecting the throat on account of their non-irritating 

 properties, and good results in this connection have been obtained 

 in cases of diphtheria. A solution of 1 in 10,000 has been found 

 to kill plague bacilli in five minutes. 



Carbolic Acid. Of all the aromatic series this is the most 

 extensively employed antiseptic. All ordinary bacteria in the 

 vegetative condition, and of these the staphylococcus pyogenes 

 is the most resistant, are killed in less than five minutes by a 

 2-3 per cent, solution in water, so that the 5 per cent, solution 

 usually employed in surgery leaves a margin of safety. But for 

 the killing of such organisms as anthrax spores a very much 

 longer exposure is necessary ; thus Koch found it necessary to 

 expose these spores for four days to ensure disinfection. The 

 risk of such spores being present in ordinary surgical procedure 

 may be overlooked, but there might be risk of tetanus spores 

 not being killed, as these will withstand fifteen hours' exposure 

 to a 5 per cent, solution. 



In the products of the distillation of coal there occur, besides 

 carbolic acid, many bodies of a similar chemical constitution, and 

 many mixtures of these are in the market the chief being cyllin, 

 izal, and lysol, all of which are agents of value. Of these lysol 

 is perhaps the most noticeable, as from its nature it acts as a 

 soap, and thus can remove fat and dirt from the hands. A one- 

 third per cent, solution is said to destroy the typhoid and cholera 

 organisms in twenty minutes. A one per cent, solution is sufficient 

 for ordinary surgical procedures. 



lodoform. This is an agent regarding the efficacy of which 

 there has been much dispute. There is little doubt that it owes 

 its efficiency to its capacity for being broken up by bacterial 

 action in such a way as to set free iodine, which acts as a 

 powerful disinfectant. The substance is therefore of value in the 



