174 ACTION OF GASES AND OF THE 
H,0,); a solution containing 0.24 per cent of H,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. 
Altehofer more recently has experimented with a solution contain- 
ing 9.7 per cent of H,O,, 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,O, 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,O, in one thousand 
of water. 
Carbon Dioxide.—The experiments of Frinkel show that certain 
bacteria grow in an atmosphere of CJ, 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,, 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 CO,. Frankel also found that the 
growth of strictly anaérobic species was restricted in an atmosphere 
of carbon dioxide. The aérobic 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,, 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 
