208 SCIENCE AND PHILOSOPHY OF THE ORGANISM 



necessary seems to render almost impossible any merely 

 chemical theory of these facts. The reaction between 

 toxin and antitoxin, albumen and precipitin is indeed 

 chemical ; it may in fact be carried out in a test-tube ; 

 but whether the production of the an ti- body itself is 

 also chemical or not could hardly be ascertained without 

 a careful and unbiassed analysis. There can be no doubt 

 that the well-known theory of Ehrlich, 1 the so-called theory 

 of side-chains (" Seitenkettentheorie ") has given a great 

 impulse to the progress of science; but even this theory, 

 irrespective of its admissibility in general, is not a real 

 chemical one : the concept of a regeneration of its so-called 

 haptophore groups is a strictly biological concept. 2 



And, indeed, here if anywhere we have the biological 

 phenomenon of adaptation in its clearest form. There are 

 very abnormal changes of the functional state of the 

 organism, and the organism is able to compensate these 

 changes in their minutest detail in almost any case. The 

 problem of the specification of the reactions leading to 

 immunity seems to me, as far as I can judge as an outsider, 

 to stand at present in the very forefront of the science. 

 There cannot be the slightest doubt that especially against 

 all sorts of foreign albumens the reaction is as strictly 

 specific as possible ; but there are some typical cases of 



1 So-called genuine or innate immunity, in contrast to the immunity 

 which is acquired, is of course a case of adaptedness only and not of adapta- 

 tion. There also exists a high degree of specific adaptedness in some animals 

 with regard to their faculty of coagulating blood. (See Leo Loeb, Biol. Bull. 

 9, 1905.) 



2 We cannot do more than barely mention here the problem of the localisa- 

 tion of anti-body production. In general it seems to be true that anti- 

 bodies are produced by those cells which require to be protected against 

 toxins ; that would agree with the general rule, that all compensation of the 

 change of any functional state proceeds from the part changed in its function.. 



