86 THE NATURE AND ORIGIN OF LIFE 



is interesting because it shows us systematically two anta- 

 gonists, each of which, if we do not know their previous 

 history, has unknown chances for victory. Our language 

 will be still more symmetrical if we use for the sheep with 

 reference to anthrax the expression we use for anthrax with 

 reference to sheep : the refractory sheep is virulent to an- 

 thrax, or the virulent anthrax is refractory to sheep 

 which is one and the same thing. 



In this symmetrical struggle the side of the anthrax bacteri- 

 dia is of more immediate interest to us ; first, because the 

 bacteridia have not the histological complexity of the sheep 

 and, consequently, our conclusions in regard to them 

 take a more simple form ; and then, because the bacteridia 

 are in the sheep and for them the sheep realizes all the 

 exterior conditions of existence. We have just noted that 

 the life of a being A could be represented symbolically by 

 the product of two factors (A x B). For the anthrax 

 bacteridia, B is the sheep. 



On the contrary, when we study the sheep, we see that 

 the anthrax with which it is inoculated is, indeed, one of the 

 factors of its medium which play an important part in the 

 life of the sheep (A) ; but it is only one of the factors. The 

 factor B comprises also atmospheric air, the grass of the 

 field, the carnivorous wolf and so on. Even though attacked 

 by anthrax, the sheep may be asphyxiated from lack of 

 oxygen or may be eaten. The life of the sheep (A) is there- 

 fore not entirely determined by the fact of the presence of 

 bacteridia in its interior, whereas the life of the bacteridia 

 finds in the sheep which contains them all the elements of the 

 factor B determining every instant their particular activity. 



For the bacteridia, therefore, the function as defined 

 is symbolically translated by the formula : 

 Bacteridia x Sheep. 



