STERILISATION 97 



spores, even after 40 days, and it was also ineffective when tried 

 against the tubercle bacillus. Further, even the more susceptible 

 Bac. typhosus could not be killed after several weeks' exposure in 

 strong solutions of common salt. The still more susceptible spirillum 

 of cholera, however, succumbed after a few hours' exposure. The 

 value of this article lies in the fact that no development of micro- 

 organisms can take place in substances covered by or immersed in it ; 

 it is a poor germicide, but an excellent antiseptic. From this it 

 follows that the consumption of diseased meat, even though salted for 

 some time, is fraught with the greatest danger. 



In addition to the gases and vapours already dealt with, we may 

 add the following remarks with regard to others : 



Oxygen is a disinfectant only in the nascent condition. 



Ozone is of no practical value. In one experiment Bacillus 

 anthracis, Staphylococcus pyogenes aureus and others, were exposed 

 for 24 hours on silk threads in an atmosphere containing 4'1 milli- 

 grammes of ozone to one litre of air ; all were quite unaffected by this 

 exposure when subsequently brought into contact with nutrient media. 

 This experiment puts ozone out of count altogether as a practical 

 disinfectant. 



Hydrogen is useless as a disinfectant. 



Carbonic Oxide. Disinfecting powers of carbonic oxide, very slight 

 and of no practical use. 



Nitrous Oxide is of no practical use. 



Nitrogen Dioxide. Several organisms tested by Frankland, viz. 

 Bac. pyocyaneus, Spirillum cholerae Asiaticae, and Spirillum Finkler- 

 Prior, were quickly killed by this gas. 



Sulphuretted Hydrogen. The experiments with this gas by different 

 observers give contradictory results, so we may safely assume that its 

 germicidal value must be so small as to be of no use for practical 

 purposes. 



Chlorine. This gas has a strong affinity for hydrogen, and, as water 

 is composed of hydrogen and oxygen, its combination with hydrogen 

 liberates oxygen, which, in the nascent condition, is, as mentioned 

 above, a powerful germicide. Hence, whilst dry chlorine is useless, 

 moist chlorine is efficient as a disinfectant. Anthrax spores can be 

 killed after exposure for one hour to an atmosphere containing four 

 per cent, chlorine, and the same can be accomplished in three hours 

 by a one per cent, solution. When the atmosphere and the spores 

 were kept dry, a percentage of 44-7 of chlorine was of no use as a 

 disinfectant. A culture containing the anthrax bacilli in the non- 



G 



