166 ACTION OF GASES AND OF THE 



H 2 O 2 ); a solution containing 0.24 per cent of H 3 O., failed to kill pus 

 cocci. But the solution used in these experiments contained also five 

 per cent of sulphuric acid, which by itself kills micrococci in the pro- 

 portion of 1 : 200. My conclusion was that, unless the chemists can 

 furnish more concentrated solutions which will keep better than that 

 with which I experimented, we are not likely to derive any practical 

 benefit from the use of hydrogen peroxide as a disinfectant. 



Altehof er more recently has experimented with a solution contain- 

 ing 9.7 per cent of H 2 O 2 , and reports the following results: He added 

 to ninety-eight cubic centimetres of hydrant water two cubic centi- 

 metres of a bouillon culture of the typhoid bacillus, and to this was 

 added sufficient of his aqueous solution of H 2 O 2 to make the propor- 

 tion present 1:1,000. At the end of twenty-four hours the bacillus 

 was proved by culture experiments to be killed. Water containing 

 the cholera spirillum, treated in the same way, was not entirely steril- 

 ized, as a few colonies developed in Esmarch roll tubes ; but the gen- 

 eral result of his experiments was that the ordinary water bacteria, 

 and the pathogenic bacteria named (cholera, typhoid) when sus- 

 pended in water, required for their destruction exposure for twenty- 

 four hours in a solution containing one part of H. 2 O 2 in one thousand 

 of water. 



Carbon Dioxide. The experiments of Frankel show that certain 

 bacteria grow in an atmosphere of C0 a as well as in the air ; among 

 these are the bacillus of typhoid fever and the pneumonia bacillus 

 of Friedlander. Other species are slightly restricted in their growth, 

 e. g. Bacillus prodigiosus, Proteus vulgaris. Still others grow only 

 when the temperature is elevated, including the pus cocci and the 

 bacillus of swine pest. Most of the saprophytic bacteria failed to 

 grow in an atmosphere of CO 2 , although their vitality was not de- 

 stroyed by it. Certain pathogenic species were, however, killed by 

 the action of this gas, among others the cholera spirillum, Bacillus 

 anthracis, and Staphylococcus pyogenes aureus. 



Leone and Hochstetter had previously reported that certain bac- 

 teria are injuriously affected by C0 2 . Frankel also found that the 

 growth of strictly anaerobic species was restricted in an atmosphere 

 of carbon dioxide. The aerobic species which failed to grow in pure 

 CO, grew abundantly when a little atmospheric oxygen was ad- 

 mitted. In the experiments of Frankland the cholera spirillum and 

 the Finkler-Prior spirillum failed to develop in an atmosphere of 

 CO 2 , and at the end of eight days were no longer capable of growth 

 when the carbon dioxide was replaced with atmospheric air. 



Carbonic Oxide. Frankland's experiments show that an atmo- 

 sphere of this gas is not favorable to the growth of the cholera spiril- 

 lum or of the Finkler-Prior spirillum, although it did not entirely 



