164 The Theory of Atmospheric Germs. [April, 



to them they re-commence their life in the same manner as 

 formerly, provided a certain degree has not been overpassed 

 in the desiccation." 



These fadts alone are sufficient to show that we must 

 rely on no prima facie or surface ideas for our conception of 

 the nature and properties of those bodies which possess 

 vitality. 



Then, as regards resistance on the part of living 

 organisms, especially with regard to temperature. 



First of all, we have direct evidence as to the influence of 

 temperatures on low organisms. We have abundant evi- 

 dence that they can support very low temperatures, very high 

 temperatures, and very rapid alternations of temperature. 

 Bacteria and monads survive a cold of 23 F. for an hour, 

 and often 5 F. for a few minutes. The lowest organisms 

 " possess for the most part," says an ardent supporter of hete- 

 rogeny, " a resistance often surprising to heat and cold." 

 An experiment of M. Pouchet shows even that certain of 

 them can easily support sudden changes of temperature, even 

 a rapid transition of ioo° C. In the hot Geyser springs 

 which reach nearly to the boiling temperature, unicellular 

 plants have been found growing. Practically, however, the 

 extreme limit of heat which it is found that developed 

 organisms can bear in the presence of water has been fixed at 

 ioo° C, i.e., the temperature of boiling water, and this by 

 the upholders of either side. In dry air, organisms are 

 capable of withstanding a considerably higher temperature 

 than when they are contained in fluids. 



In the ovum and spore condition, life-possessing matter, 

 according to all the evidence, possesses a higher power of 

 resistance than obtains in case of the developed organism. 

 The zoosperms of the frog can retain their vitality in a 

 cold not exceeding 24 below freezing. M. Payen deter- 

 mined that the sporules of the oidium aurantiacum resisted a 

 moist heat of 248 F., and only lost their faculty of germina- 

 tion at a heat of 284 F. Pasteur asserted that spores of 

 mildew in vacuo or dry air were fertile after exposure 

 for twenty minutes to half an hour to a temperature of 

 from 248 F. to 257 F., but he concluded that exposure for 

 more than twenty minutes to 260 F. to 266 F. completely 

 destroyed their vitality. It is thus seen that organised 

 material in the embryonic condition is capable of resisting 

 temperatures which seem at first sight almost impossible. An 

 argument to the contrary has, however, been urged from the 

 behaviour of known and recognised spores under such con- 

 ditions. Pouchet observed that the spores of Ascophora, 



