THE SCOPE OF BIOLOGY 17 



previously reached by others; but Tyndall proved definitely 

 that while a temperature below boiling is sufficient to kill 

 active germs, the spores stand a temperature of boiling for a 

 long time, and hence boiling does not sterilize liquids. Since 

 previous experimenters had assumed that all life was destroyed 

 by boiling, they had been contented with the simple boiling 

 of the liquid to eliminate any organisms that might have been 

 there originally. If, therefore, any of these resisting spores 

 chanced to be in their solutions, they would subsequently 

 develop; and from this fact the experimenter might reach the 

 erroneous conclusion that the living organisms coming from 

 these spores developed spontaneously. Tyndall carefully 

 eliminated all of these errors and established the following 

 important conclusions. No evidence for spontaneous genera- 

 tion exists and the success of an experimenter in obtaining 

 any evidence of spontaneous generation is in inverse propor- 

 tion to the care with which he performs his experiments. 



This statement has stood almost unquestioned by biol- 

 ogists since it was first promulgated in 1875; and during 

 the last thirty years the work of thousands of experimenters 

 in the science of bacteriology has only confirmed the accuracy 

 of Tyndall's conclusion. 



We must accept the fact that whenever any living animal 

 or plant, no matter how small, makes its appearance in a 

 solution, originally there was present in this solution a living 

 germ which started the development of the organism by the 

 process of ordinary reproduction and growth. At the present 

 time, therefore, there is no shred of evidence that, under any 

 conditions which we can produce, life can arise spontaneously. 



The Primal Origin of Life. The conclusion that spontaneous 

 generation does not occur to-day, leaves unanswered the ques- 

 tion of the primal origin of life. It has been a disappointment 

 to biologists to be obliged to admit that they can find no evi- 

 dence for the theory of spontaneous development, since at some 

 period in the history of the world, life must have made its 



