HALOID ELEMENTS UPON BACTERIA. 175 
prevent development, and after seven days’ exposure the spirilla were 
not all killed, although a comparatively small number of colonies de- 
veloped. Bacillus pyocyaneus failed to grow in an atmosphere of 
CO, but when air was admitted, at the end of seven or eight days, 
abundant development occurred. 
Methane, CH,—We have no exact experiments to determine 
the action of marsh gas in a pure state on bacteria, but the experi- 
ments of Kladakis upon illuminating gas may be taken as repre- 
senting approximately what might be expected from exposure in 
pure CH,. An analysis of the gas used in his experiments showed 
it to contain 37.97 per cent of hydrogen, 39.37 per cent of methane 
(CH,), 9.99 per cent of nitrogen, 4.29 per cent of ethene (C,H,), 3.97 
per cent of carbonic oxide (CO), 0.61 per cent of oxygen, and 0.41 per 
cent of carbon dioxide. As hydrogen and nitrogen are neutral, and 
carbonic oxide is shown by the experiments of Frankland not to act 
as a germicide after several days’ exposure to its action, the positive 
results obtained in the experiments of Kladakis may be ascribed to 
the presence of CH, (39.37 per cent) or of C,H, (4.29 per cent), or of 
both together. 
A large number of microérganisms were tested, and among these 
Proteus vulgaris alone grew in an atmosphere of illuminating gas. 
The others not only failed to grow in such an atmosphere, but were 
destroyed by it. Cultures of Bacillus anthracis, Staphylococcus pyo- 
genes aureus, and Spirillum cholerze Asiaticee were sterilized in half 
an hour by the action of this gas. The gas was also found to be un- 
suitable for anaérobic cultures. 
Nitrous Oxide, N,O.—The experiments of Frankland, made 
upon the cholera spirillum, the spirillum of Finkler-Prior, and the 
bacillus of green pus, gave results similar to those obtained with CO, 
viz., seven days’ exposure in an atmosphere of this gas failed to de- 
stroy the test organisms, but completely restrained the growth of 
Bacillus pyocyaneus and interfered materially with the development 
of the two species of spirillum without entirely preventing it. 
Nitrogen Dioxide, NO.—Frankland found that his test organ- 
isms were quickly killed by this gas (Bacillus pyocyaneus, Spirillum 
cholerz Asiatic, Spirillum Finkler-Prior). 
Hydrosulphurtc Acid, H,S.—In the experiments of Frankland 
this gas proved to be quickly fatal to the bacteria tested (Bacillus 
pyocyaneus, Spirillum cholere Asiaticee, Spirillum Finkler-Prior). 
On the other hand, Grauer found that this gas did not exercise any 
injurious influence upon the tubercle bacillus, the bacillus of anthrax, 
the typhoid bacillus, or the cholera spirillum, after the exposure of 
these microédrganisms in a current of the gas for an hour. 
It has been shown by the experiments of Holschewnikoff and 
