PRACTICAL DIRECTIONS FOR DISINFECTION. 215 



it is known that recent researches have demonstrated that many of the 

 agents which have been found useful as deodorizers or as antiseptics are en- 

 tirely without value for the destruction of disease germs. 



" This is true, for example, as regards the sulphate of iron, or copperas, a 

 salt which has been extensively used with the idea that it is a valuable dis- 

 infectant. As a matter of fact, sulphate of iron in saturated solution does 

 not destroy the vitality of disease germs, or the infecting power of material 

 containing them. This salt is, nevertheless, a very valuable antiseptic, and 

 its low price makes it one of the most available agents for the arrest of putre- 

 factive decomposition" (op. cit., p. 237). 



Chloride of lime is also a valuable antiseptic and deodorant, and I know 

 of 110 objection to substituting it for sulphate of iron other than the question 

 of cost. The first cost of chloride of lime, by the quantity, is about double 

 that of sulphate of iron, but practically the difference is much greater, be- 

 cause it is necessary to preserve the chloride of lime in air-tight packages. 

 When exposed to the air it deteriorates in value very rapidly. It is, there- 

 fore, necessary to pack it in air-tight receptacles which will not be injured 

 by the corrosive action of free chlorine, and in comparatively small quanti- 

 ties so that the contents of a package may be used soon after it is opened. 



We now proceed to consider the experimental data relating to the germi- 

 cidal value of chloride of lime. 



The Committee on Disinfectants gave it "the first place for disinfecting 

 excreta, on account of the rapidity of its action." This recommendation was 

 upon experimental data obtained in the pathological laboratory of the Johns 

 Hopkins University, under the writer's direction, and is sustained by more 

 recent experiments made in Germany. 



The experiments of Bolton, made for the Committee on Disinfectants in 

 1886, j-ave the following results : The time of exposure being two hours, the 

 typhoid bacillus and cholera spirillum in bouillon cultures were killed by a 

 solution containing one part to one thousand parts of water (containing 0.03 

 per cent of available chlorine). Anthrax spores were killed in the same time 

 by a solution containing 0.3 per cent of available chlorine. Typhoid faeces 

 were sterilized by a two-per-cent solution, and in several instances by a one- 

 lialf-per-cent solution ; but some resistant spores of non-pathogenic bacilli sur- 

 vived in two experiments in which a solution of 1 : 100 was used. In bouillon 

 cultures to which ten per cent of dried egg albumin had been added the 

 typhoid bacillus was destroyed by one-half per cent (1 : 200). 



Nissen, whose experiments were made in Koch's laboratory in 1890, found 

 that anthrax spores were destroyed in thirty minutes by a five-per-cent 

 solution, and in seventy minutes by a one-per-cent solution. In his experi- 

 ments the typhoid bacillus and the cholera spirillum were destroyed with 

 certainty in five minutes by a solution containing 0.12 per cent (1: 833) ; the 

 anthrax bacillus in one minute by 1 : 1, 000 ; Staphylococcus pyogenes aureus in 

 one minute by 1 : 500. Experiments made by the same author on the sterili- 

 zation of f;eces showed that one per cent could be relied upon to destroy the 

 bacillus of typhoid fever and the spirillum of cholera in faeces in ten min- 

 utes. 



Carbolic Acid The Committee on Disinfectants says: " A five-per-cent 

 solution of carbolic acid may be used instead of the chloride of lime solution, 

 the time of exposure to the action of the disinfectant being four hours." 

 This recommendation is made in view of the fact that in those diseases in 

 which it is most important to disinfect the excreta the specific germ does not 

 form spores. This is now believed to be true of the typhoid bacillus, the 

 spirillum of cholera, the bacillus of diphtheria, the bacillus of glanders, and 

 the streptococcus of erysipelas ; and it has been shown by exact experiments 

 that all of these pathogenic bacteria are destroyed in two hours by a one-per- 

 cent solution, or less, of this agent. 



Spores require for their destruction a stronger solution and a longer time. 

 Koch found a one-per-cent solution to be without effect on anthrax spores 

 after fifteen days' exposure ; a two-per-cent solution retarded their develop- 



