DEFENSIVE FERMENTS OF THE ANIMAL ORGANISM 37 



repeatedly indicated before, all the cells stand in 

 actively reciprocal relations with each other. We 

 have plenty of proofs for the acceptance of this view ; 

 while, on the other hand, we have no clear insight, 

 at present, into the signification of this reciprocal 

 dependence. Probably unicellular organisms alone 

 are wholly dependent upon themselves. They per- 

 form all the processes necessary for life independently 

 of other cells, except when, as sometimes happens, 

 a conjunction of these simple organisms rises to the 

 level of a symbiosis. The latter, as we have already 

 pointed out, must have a value corresponding exactly 

 }l o the reciprocal interactions of the cells of the more 

 highly organized forms of the vegetable and animal 

 kingdoms. For there is no doubt that in plants, too, 

 the cells have actively reciprocal relations. 



Doubtless there are, in an organism composed of 

 cell groups, numerous kinds of cells which can 

 live without having reciprocal relations with other * 

 cells, exactly in the same way as a single individual 

 can isolate itself from its stock and still continue life 

 for a certain time. But in the same manner as the 

 well-being of a people or a State finally depends 

 upon the regular collaboration of the many, so each 

 kind of cell expresses its full value only by associating 

 its work with that of the other cells in the organism. 

 Only then is a cell capable of developing all 

 its capacities. In many particular functions, indeed, 



