HISTORY OF COLD AND THE ABSOLUTE ZERO. 239 



power of the inetals .coiTld be expres.sed l)v a linear function of the 

 al)S()lute temperature, hut at ' the extreme range of temp<'rature now 

 under consideration this hiw was found not to hold o(Mierally; and, 

 further, it appeared that many al)rupt electric changes take place, 

 which originate probably from specific molecular changes occurring 

 in the metal. The thermo-electric neutral points of c(M-tain metals, 

 such as lead and gold, which are located at or below the ])oiling point 

 of hydrogen, have l)een found to l)e a convenient means of defining 

 specific temj^eratures in this exceptional part of the thermo-metric 

 scale. 



The effect of cold upon the life of living organisms is a matter 

 of great intrinsic int(M-est, as well as of wide theoretical impor- 

 tance. Experiment indicates that moderately high tcMuperatures 

 are much more fatal, at least to the lower forms of life, than are 

 exceedingly low ones. Professor McKendrick froze for an hour 

 at a temperature of 182° C. samples of meat, milk, etc., in sealed 

 tu]»es. When these were opened after lieing kept at blood lieat for 

 a few days their contents were found to l)e quite putrid. More 

 recently some more elaborate tests were carried out at the flenner 

 Institute of Preventive Medicine on a series of typical liacteria. 

 These were exposed to the temperature of licjuid air for twenty 

 hours. ])ut their vitality was not affected, their functional activities 

 I'cmained unin)paired, and the cultures which they yielded weiv normal 

 in every respect. The same result was obtained when licpiid hydrogen 

 was substituted for air. A similar persistence of life in seeds has 

 been demonstrated even at the lowest temperatures. They were 

 frozen for over a hundred hours in liquid air, at the instance of 

 Messrs. Brown and Escoml>e, with no other result than to afi'ect their 

 protoplasm with a certain inertness, from which it recovered with 

 warmth. Subsequently connnercial samples of barley, pea, vegetable- 

 marrow, and mustard seeds were literally steeped for six hours in 

 li(iuid hydrogen at the Royal Institution, yet when they were sown by 

 Sir W. T. Thiselton Dj^er at Kew in the ordinary way the proportion 

 in which germination occurred was no less titan in the other batches of 

 the same seeds which had suti'ered no abnormal treatment. Bacteria 

 are minute vegetable cells, the standard of measurement for which is the 

 '' mikron." Yet it has been found possible to completely triturate these 

 microscopic cells wdien the operation is carried out at the temperature 

 of liquid air, the cells then being frozen into hard, breakable masses. 

 The typhoid organism has been treated in this way and the cell plasma 

 obtained for the purpose of studying- its toxic and immunizing- prop- 

 erties. It would hardly have been anticipated that liquid air should 

 find such immediate application in biological research. A research by 

 Professor Macfadyen," just concluded, has shown that many n arieties 



« Note by author, April 16, 190;-5. This important paper has recently appeared in 

 the Proceedings of the Royal Society. 



