HALOID ELEMENTS UPON BACTERIA. 167 



prevent development, and after seven days' exposure the spirilla were 

 not all killed, although a comparatively small number of colonies 

 developed. Bacillus pyocyaiius 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 4 . 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 4 . 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 4 ), 9.99 per cent of nitrogen, 4.29 per cent of ethene (C a H 4 ), 3.97 

 per cent of carbonic oxide (CO), O.G1 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 4 (39.37 per cent) or of C 2 H 4 (4.29 per cent), or of 

 both together. 



A large number of microorganisms 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 cholerse Asiaticse were sterilized in half 

 an hour by the action of this gas. The gas was also found to be un- 

 suitable for anaerobic cultures. 



Nitrous Oxide, N 2 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 pyocyanus 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 pyocyanus, Spirillum 

 cholerse Asiaticse, Spirillum Finkler-Prior). 



Hydrosulphuric Acid, H 2 S. In the experiments of Frankland 

 this gas proved to be quickly fatal to the bacteria tested (Bacillus 

 pyocyanus, Spirillum cholerse Asiaticse, Spirillum Finkler-Prior). On 

 the other hand, Grauer found that this gas did not exercise any in- 

 jurious influence upon the tubercle bacillus, the bacillus of anthrax, 

 the typhoid bacillus, or the cholera spirillum, after the exposure of 

 these microorganisms in a current of the gas for an hour. 



It has been shown by the experiments of Holschewnikoff and 



