48 THE NATURE AND ORIGIN OF LIFE 



for us if we consider cases in which the identity of the original 

 substance and of the final substance appears with greater 

 evidence. 



I sow a grain of wheat ; I get from it a wheat ear with 

 forty grains ; then I sow these forty grains and get sixteen 

 hundred ; thus, by two years' cultivation, I realize a pro- 

 duction from the original one grain of wheat, at the expense 

 of soil and atmosphere, of sixteen hundred grains whose sub- 

 stance seems to me very close to that of the original grain. 



A more perfect example may be found in bacteria-culture 

 as it is practised in laboratories. When a given bacterium 

 has been well studied, when we know all its needs in respect 

 to food, air, temperature, we succeed after minute care in 

 obtaining a prodigious multiplication of the bacterium ; and 

 we can preserve in its descendants, with the utmost exactness 

 and detail, all the characters which had been brought out in 

 the laboratory experiments. 



In such a case the law appears without any vagueness of 

 outline. The bacterium has assimilated its culture-medium, 

 has transformed parts of this culture-medium into bacteria 

 like to itself. If, then, we pass over the consideration of 

 the form of the bacteria, if we attend solely to the substances 

 which constitute the bacteria, we find a result of chemical 

 order a chemical reaction novel in its results and belonging 

 to no not-living body. 



Not-living bodies, not-living chemical compounds, are 

 always destroyed by reacting chemically with other com- 

 pounds. If we agree to take account only of the quantities 

 of substance which have effectively undergone reaction, an 

 equation of chemistry will always present itself, roughly, 

 as follows : 



A -fB=C + D 



2NaCl + H 2 So 4 -. = Na 2 So 4 + 2HC1 



