148 ANTISEPTICS 



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 creolin, 

 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 1 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 treatment 

 of foul wounds, such as those of the mouth and rectum, where 

 reducing bacteria are abundantly present. It acts more slightly 

 where there are only pyogenic cocci, and it seems to have a 

 specially beneficial effect in tubercular affections. In certain 

 cases its action may apparently be aided by the presence of the 

 products of tissue degeneration. 



From the results which have been given it will easily be 

 recognised that the choice of an antiseptic and the precise 

 manner in which it is to be employed depend entirely on the 

 environment of the bacteria which are to be killed. In many 

 cases it will be quite impossible, without original inquiry, to say 

 what course is likely to be attended with most success. 



