34 THE BEGINNINGS OF LIFE. 



of accidental impurities, I am inclined to think that 

 such compounds may require an admixture of some 

 more unstable substance before living things are capable 

 of being evolved. This more unstable substance 

 (existing as ^dead' organic matter) may act as a 

 ferment and may initiate changes which would not 

 occur if the saline substance existed alone in solution i. 

 Certainly, in my experiments, 1 have been able to find 

 no valid evidence that living things have presented 

 themselves without such admixture. Minute fragments 

 of vegetable fibre of different kinds — which it is nearly 

 impossible altogether to exclude — have almost inva- 

 riably been present in the saline solutions employed. 

 Such fragments are, indeed, constantly present within 

 the crystals of ammonic tartrate which I have em- 

 ployed; whilst other evidence, previously alluded to, 

 makes it probable that the crystals themselves contain 

 a ferment. Thus, a solution of ammonic tartrate 

 with some sodic phosphate when not previously heated, 

 rapidly becomes turbid on exposure to the air or In 



^ Just as motion (produced by constant slight shocks) amongst the 

 molecules of amorphous iron favours the lapse of these into crystalline 

 modes of aggregation, so may motion amongst the particles of a saline 

 compound tend to disturb existing modes of combination, and facilitate 

 the assumption of new modes of combination, towards the occurrence of 

 which there is a natural tendency. And, as Liebig says : — ' All organic 

 substances become excitors of fermentation, as soon as they pass into a 

 state of decomposition : the changing condition once imparted, propa- 

 gates itself in every organic atom, which is not itself, that is, by its own 

 inherent energy, capable of annihilating the imparted motion by pre- 

 senting an adequate resistance.' (' Letters on Chemistry,' p. 208.) 



