Xxviii THE BEGINNINGS OF LIFE. 



answer to this, I can only call attention to the fact, that 

 changes of this kind must have taken place ' spontaneously ' 

 in the fluids within the experimental tubes which, after having 

 been submitted to temperatures varying from 133-! 53 C. 

 for variable periods, were nevertheless subsequently found to 

 contain living organisms. We are compelled to come to this 

 conclusion, not only because there is not one tittle of evidence 

 at present existing to show that any living thing could live 

 through such an exposure, but because there are very strong 

 reasons indeed which should suffice to convince us, that no 

 living thing could be subjected to such a temperature without 

 its life being certainly destroyed. Therefore, in these cases, 

 the particular molecular re-arrangements must have been 

 initiated without the intervention of living ferments, and they 

 are thus comparable with those that are known to take place 

 in a solution of cyanate of ammonia. Here ' spontaneously/ 

 or with the aid of a little heat only, a molecular re-arrange- 

 ment occurs, and the saline cyanate of ammonia is replaced 

 by a totally different, though isomeric compound, urea. In 

 order to effect this transformation, no living agency is neces- 

 sary none has even been supposed to exist ; and there is no 

 more really cogent reason why we should imagine such an 

 agency to be necessary, in order that tartrate of ammonia 

 may undergo a more or less similar isomeric transformation. 

 (d). We find, moreover, different kinds of living things 

 associated with different sets of conditions. In none of the 

 crystals of tartrate of ammonia have I ever found a single 

 distinct Bacterium, and there has been the same complete 

 absence of organisms of this kind in all my experimental 

 fluids containing ammonic tartrate and sodic phosphate, 

 which have been sealed in airless flasks. This agreement is 

 very striking, seeing that whenever a similar fluid, or a solu- 

 tion of tartrate of ammonia alone, is exposed to the air, 

 Bacteria appear in abundance. There is a marked accord- 



