The Conditions of Life and Death. 93 



of hard ice, and survived. And although it is usually 

 said that a temperature a little below freezing point, 

 say ~4C., inside the body of an organism certainly 

 means death, Raoul Pictet, who has had much experience 

 with low temperatures, found that frogs might survive 

 - 28 C., snails - 120 C., and bacteria - 200 C. 



About 47 C. is usually mentioned as the temperature 

 which infallibly kills the living matter of ordinary plant- 

 cells in water, and less is usually sufficient to kill small 

 animals in water; yet there are hot springs in which 

 both plants and animals flourish at about 50 C., and 

 the spores of the anthrax bacillus are able to survive 

 exposure to over 100 C. 



Similarly, there are limits of pressure to be con- 

 sidered ; but we need not go further. From our present 

 historical point of view we have only to notice that 

 much interesting experimental work has been done in 

 recent years in determining the limits of vitality in 

 relation to such essentials as food, moisture, oxygen, 

 heat, and pressure, the general result being to intensify 

 our impression of the plasticity of life. 



If it were the object of this book to give a statement 

 of the established facts of biology, our discussion of the 

 origin of life might be condensed into a origin 

 single sentence : we do not know anything of Life - 

 in regard to the origin of life. The only certainty is a 

 negative one there is no established case in which liv- 

 ing organisms have arisen apart from parent organisms 

 of the same kind. But as the whole aim of the book is 

 historical, and as the problem of the origin of life has 

 bulked largely in the history of biology much more 

 largely in the past than it does now ; and as, moreover, 

 the biology of the Victorian Era claims to have finally 

 dismissed, not the possibility of, but all pretended 

 instances of spontaneous generation, it seems in keep- 

 ing with our purpose to devote a few pages to some 

 account of the long-drawn-out discussion. 



If the longevity of a belief were an index to its truth, 

 the theory of spontaneous generation should rank high 

 among the veracities, for it flourished throughout twenty 

 centuries and more. We cannot trace the history of 



