the Tempemture of Liqiiicl Air on Bacteria. 181 



liquid air (- 183° C. to - 192° C). The results were equally nega- 

 tive in the recent experiments of Sir W. Thiselton-Dyer,* in which 

 seeds survived exposure for upwards of six hours to the temperature 

 of liquid hydrogen ( - 250° C. to - 252° C). 



The following investigation on the influence of the temperature of 

 liquid air on bacteria, was carried out at the suggestion of Sir James 

 Crichton Browne and Professor Dewar. The necessary facilities were 

 most kindly given at the Eoyal Institution. The experiments were 

 conducted under the personal supervision of Professor Dewar, and he 

 has asked me to put the results on record, although it must be 

 acknowledged that the essential features of the investigation are due 

 to him. 



The bacteria employed were selected from the stock of the Jenner 

 Institute of Preventive Medicine, where the results were also con- 

 trolled. Piu-e cultures of the several micro-organisms were employed, 

 and the series included typical representatives of saprophytic and 

 parasitic bacteria. The organisms chosen possessed varying degrees of 

 resistance to external agents — the extremes in this respect being repre- 

 sented by the very sensitive spirillum of Cholera Asiatica and the 

 highly resistant spores of B. anthracis. 



Ten organisms were used for the experiments, viz. : — B. typhosus, 

 B. coli communis, B. diphtherice, Spirillum cJiolerce Asiaticce, B. proteus 

 vulgariSy B. acidi lactici, B. anthracis (sporing culture), Staphylococcus 

 pyogenes aureus, B. pliosphorescens and Photobacferium balticum. 



The cultures of the organisms were young and vigorous, and were 

 tested both on solid and in fluid media, viz. : — Nutrient gelatin, agar- 

 agar, potato and peptone broth. 



The cultures on these media were simultaneously exposed to the 

 temperature of liquid air for twenty hours (- 182° C. to - 190° C). 

 They -were then carefully thawed and examined. The results may 

 be briefly stated. In no instance, whether on solid or in liquid media,, 

 could any impairment of the vitality of the micro-organisms be 

 detected. The fresh growths obtained from the exposed tubes were 

 normal in every respect, and the functional activities of the bacteria 

 were equally unaff'ected. The colon bacillus produced its typical 

 eff'ects — such as the curdling of milk, the fermentation of sugar and 

 the production of indol ; the Staphylococcus pyogenes aureus retained its 

 pigment producing properties and the anthrax spores their pathogenic 

 action on animals. The photogenic bacteria preserved their normal- 

 luminous properties. These photogenic properties are intimately 

 connected with the functional activities of the cells. The cells emit 

 light which is apparently produced by a chemical process of intra- 

 cellular oxidation and the phenomenon ceases with the cessation of 

 their activity. These organisms therefore furnished a very happy 



* ' Eoy. Soc. Proc.,' vol. 65, 1899, p. 361. 

 VOL. LXVI. Q 



