ADAPTATION 209 



specificity in the production of antitoxins also. It is, of 

 course, the fact of specific correspondence between stimulus 

 and reaction, that gives to immunity its central position 

 among all adaptations, no matter whether the old hypothesis 

 of the production of specific anti-bodies proves tenable, or 

 whether, as has been urged more recently by some authors, 

 the anti-body is always the same but reacts differently 

 according to the medium. In the latter case it would be 

 the medium that is regulated in some way by the organism 

 in order to attain a specific adaptedness. 



NO GENERAL POSITIVE RESULT FROM THIS CHAPTER 



But now let us look back to the sum of all the physio- 

 logical reactions studied, and let us see if we have gained 

 a new proof of the autonomy of life from our long chapter. 



We freely admit we have not gained any really new 

 proof, but we may claim, I think, to have gained many 

 indicia for the statement that the organism is not of the 

 type of a machine, in which every single regulation is to 

 be regarded as properly prepared and outlined. 



It is precisely in the field of immunity that such a 

 machine -like preparation of the adaptive effects seems 

 almost impossible to be imagined. How indeed could there 

 be a machine, the chemical constituents of which were such 

 as to correspond adaptively to almost every requirement ? 

 to say nothing of the fact that the production of more of 

 the protecting substance than is actually necessary could 

 hardly be said to be " chemical." 



In fact, we are well entitled to say that we have reached 

 here the very heart of life and of biology. If nevertheless 



14 



