186 ORIGIN AND NATURE OF LIFE 



and for those compounds of many hundreds 

 of atoms which are characteristic of life, the 

 range is narrowly limited. 



Thus, all the life of the planet would be 

 destroyed at a temperature which we may 

 place for absolutely inclusive purposes at 

 56°C. At about ten degrees below this 

 temperature all birds and all mammals would 

 cease to exist. The other species would 

 have perished long before, the vast bulk 

 perishing at 25° to 30° C, which is below 

 human blood heat. Even those highly organ- 

 ized ferments, called enzymes, which, when 

 separated from the living cell that bore 

 them, still bear half-impressed upon them 

 certain living properties — all these suffer 

 rapid deterioration in all known cases at 

 50° C, and at 60° to 70° C. they are rapidly 

 destroyed. 



Since sedimentary rocks would begin to be 

 deposited soon after the surface temperature 

 of the earth had fallen below the temperature 

 of boiling water, viz., 100° C, the early 

 appearance of fossil remains in the older 

 sedimentary rocks, when due allowance has 

 been made for the geological time necessary 

 for the earth's surface to cool from boiling 

 point to the life-temperature, demonstrates 

 the important point that as soon as tempera- 



