MORE ABOUT SUSPENDED ANIMATION 187 



of liquid hydrogen (252 degrees below zero centigrade). 

 These bacteria may be obtained by selective cultivation 

 from sea-water taken on the coast, in which a few are 

 always scattered. A rich growth of these bacteria in 

 gelatine broth gives off a brilliant greenish light when 

 shaken with atmospheric air or otherwise exposed to 

 oxygen. The light is so intense that a glass flask holding 

 a pint of the cultivation gives off sufficient light to enable 

 one to read in an othej;wise dark room. The emission of 

 light is dependent on the chemical activity of the living 

 bacteria in the presence of oxygen. In the absence of 

 free oxygen they cease to be luminous. As soon as they 

 •are killed the light ceases. When they are frozen solid 

 the light ceases, even in the presence of free oxygen gas. 

 When a film consisting of such a culture is frozen solid it 

 will remain inactive if the low temperature be maintained 

 for months, thougl^ exposed to free oxygen gas, and then, 

 as soon as it is liquefied by a gentle rise in temperature, 

 the active changes recommence, and the phosphorescent 

 light beams forth. Sir James Dewar exposed such films 

 to the low temperature of liquid hydrogen for (so far as I 

 remember) six months, and obtained from them at once 

 the evidence of their living chemical activity, namely, their 

 " phosphorescence," as soon as they were thawed. In the 

 frozen state, at a temperature of minus 250 degrees centi- 

 grade, nothing, it appeared, could injure these phosphor- 

 escent bacteria. No chemical can " get at them " at that 

 temperature, the most biting acid, the most caustic alkali 

 cannot touch them when, like them, it is in a hard, solid 

 condition. Powdering the film by mechanical pressure 

 has no effect on the bacteria. > They are too small to be 

 crushed by any mill. Such germs would, it seemed, surely 

 be able to travel through interstellar space, as suggested 

 by Kelvin. 



Then it occurred to Sir James that light — the strangely 



