THE ACTIONS OF CERTAIN ANTISEPTICS. 147 



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 i per 

 cent solution is sufficient for ordinary surgical procedures. 



Iodoform. — 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 power- 

 ful disinfectant. The substance is therefore of value in the 

 treatment of foul wounds, such as those of the mouth and rec- 

 tum, 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 rec- 

 ognised that the choice of an antiseptic and the precise man- 

 ner 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. 



