ACTION OF GASES AND HALOID ELEMENTS UPON BACTERIA. 173 



Wyssokowicz found that the presence of ozone in a culture me- 

 dium restrained the development of the anthrax bacillus, the bacillus 

 of typhoid fever, and others tested, but concludes that this is rather 

 due to the oxidation of bases contained in the nutrient medium than 

 to a direct action upon the pathogenic bacteria. 



Sonntag, in his carefully conducted experiments, in which a cur- 

 rent of ozonized air was made to pass over silk threads to which were 

 attached anthrax spores, had an entirely negative result. The an- 

 thrax bacillus from the spleen of a mouse, and free from spores, was 

 then tested, also with a negative result, even after exposure to the 

 ozonized air for twenty minutes at a time on four successive days. In 

 another experiment several test organisms (Bacillus anthracis, Bacil- 

 lus pneumonise of Friedlander, Staphylococcus pyogenes aureus, 

 Staphylococcus pyogenes albus, Bacillus murisepticus, Bacillus 

 crassus sputigenus) were exposed on silk threads for twenty-four 

 hours in an atmosphere containing 4. 1 milligrammes of ozone to the 

 litre of air (0. 19 volumes per cent). The result was entirely negative. 

 When the amount was increased to 13.53 milligrammes per litre the 

 anthrax bacillus and Staphylococcus pyogenes albus failed to grow 

 after twenty-four hours' exposure. The conclusion reached by Nis- 

 sen, from his own experiments and a careful consideration of those 

 previously made by others, is that ozone is of no practical value as a 

 germicide in therapeutics or disinfection. 



Hydrogen. This gas has no injurious effect upon bacteria, as is 

 shown by the fact that the anaerobic and facultative anaerobic species 

 grow readily in an atmosphere of pure hydrogen. 



Hydrogen peroxide in solution in water is a valuable antiseptic 

 and deodorant, but its value as a germicide has been very much 

 overestimated. Miquel, in his experiments to determine the anti- 

 septic value of various agents, places H 2 O 2 third in the list of " sub- 

 stances eminently antiseptic," and states that it prevents the develop- 

 ment of the bacteria of putrefaction in the proportion of 1: 20,000. 



In the writer's experiments (1885) a solution was used which 

 contained at first 4. 8 per cent of H 2 O 2 , and five per cent of sulphuric 

 acid which was added by the chemist who prepared the solution, to 

 prevent loss of the hydrogen peroxide. At the end of a month the 

 amount of H 2 O 2 was again estimated, and found to be 3.98 per cent. 

 Five weeks later the proportion was 2.4 per cent. Tested upon 

 ^broken-down" beef tea, this solution was found to destroy the 

 vitality of the bacteria of putrefaction contained in it, in two hours 7 

 time, in the proportion of thirty per cent (about 1.2 per cent of H 2 2 ). 

 Anthrax spores were killed in the same time by a twenty-per-cent 

 solution (0.8 per cent H 2 O 2 ). Tested upon a pure culture of pus 

 cocci, it was active in the proportion of ten per cent (0.4 per cent of 



