172 ANTISEPTICS 



vibrio in one hour, diphtheria bacillus in three hours, the staphylococcus 

 pyogenes in six hours, and anthrax spores in thirteen hours. In the case 

 of organisms which have become dry it is probable, however, that much 

 longer exposures are necessary, but on this point we have no definite 

 information. 



Formalin gas has only a limited application ; it has little effect on dry 

 organisms, and in the case of wet organisms, in order to be effective, 

 probably must become dissolved so as to give the moisture a proportion 

 analogous to the strengths stated above with regard to the vapour. 



Sulphurous Acid. — This substance has long been in use, largely from 

 the cheapness with which it can be produced by burning sulphur in the 

 air. An atmosphere containing "98 per cent, will kill the pyogenic cocci 

 in two minutes if they are wet, and in twenty minutes if they are dry ; 

 and anthrax bacilli are killed by thirty minutes' exposure, but to kill 

 anthrax spores an exposure of from one to two hours to an atmosphere 

 containing 11 per cent, is necessary. For a small room the burning of 

 about a pound and a half (most easily accomplished by moistening the 

 sulphur with methylated spirit) is usually considered sufficient. It has 

 been found that if bacteria are protected, e.g., when they are in the 

 middle of small bundles of clothes, no effect is produced even by an 

 atmosphere containing a large proportion 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 con' 

 nection 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 ^s 

 sufficient for ordinary surgical procedures. 



