and that Sldph i/hndccus pi/iK/ciics ulhiis and llii' liihcrcle 

 hdcilhis could wil lislaiid llic same temperature I'oi* 50 

 hours. In I'urllici' ('.\])('rimeiits, the same invest i^'ator 

 re])orted tlial these ori;anisms were not killed after two 

 consecutive exposures of respectively 4 hours at - 268.8° 

 and li/> hours at - 271.8°. Cooling was relatively slow, it 

 rtM|uiiin,i;' al>out 24 hours for the entire experiment. 



Zirpolo (1!).')2) observed no injurious effect when 

 lumiiK'scent l)acte]'ia {Bacillus and Micrococcus picran- 

 tonii), in the fresh vegetative state, were exposed for sev- 

 eral hours to the temperature of liquid helium. 



Lipman (1936a) immersed in liquid helium, at tempera- 

 tures varying from 4.2° K to 1.35° K, spores of common 

 bacilli (species not mentioned), smeared on fragments of 

 cover glasses, and desiccated for 2 weeks. The prepara- 

 tions were kept 2 hours at the lowest temperature and 42 

 hours below 4.2° K. The spores presented as abundant 

 a bacterial growth as would normal spores. 



We shall not review here the literature accumulated 

 during the last 3 years on the method of drying bacteria 

 at low temperatures for preserving them. We shall men- 

 tion only that, in these experiments, the physiological 

 properties of the organisms were found unimpaired (Cf. 

 the fundamental work of Flosdorf and Mudd, 1935). 



B. Park, Williams and Krumwiede ("Pathogenic 

 Microorganisms," 8th ed. p. 698, New York, 1924) kept 21 

 strains of water-inoculated B. typhosus at about -2° to 

 - 7°. Six cultures were sterile after 5 weeks and all were 

 sterile after 22 weeks. 



Hilliard, Torossian and Stone (1915) and Hilliard and 

 Davis (1918) subjected water suspensions of B. coli to 

 freezing for 3 hours at 0° or at - 15° and determined the 

 percent of survivors by the usual method of bacterial 

 counts. At 0°, 26.4% to 67.77r, and at -15°, 99.4% to 

 99.7% of the organisms were killed. After intermittent 

 freezing for the same length of time (4 freezings), the 

 number killed was slightly greater. 



