ADAPTATION 189 



ON CERTAIN PRE-REQUISITES OF ADAPTATIONS IN GENERAL 



We are thinking of the general and important question, 

 what types of adaptations may be expected in the field of 

 physiology and whether there may be certain classes of 

 regulatory events which possibly might be expected to occur 

 in the organism on a priori grounds, but which, never- 

 theless, are to be regarded as impossible after a more 

 intimate analysis of its nature, even at the very beginning ? 

 Or, in other words, to what kinds of changes of the medium 

 will an organism be found able or unable to adapt itself? 



We know that the state of functioning must be altered 

 in order to call forth any sort of adaptation at all. Now, 

 there can be no doubt that a p"iori it would seem to be 

 very useful for the organism, if it never would let enter into 

 its blood, lymph, etc., be it through the skin or through the 

 intestine, any chemical compound that would prove to be a 

 poison afterwards. In fact, a man, judging on the principle 

 of the general usefulness of all the phenomena of the living, 

 might suppose that there would exist a sort of adaptation 

 against all poisons to the extent that they would never be 

 allowed to enter the real interior of the body. We know 

 that such reasoning would be incorrect. But we also can 

 understand, I suppose, that an a priori analysis of a more 

 careful kind would have reasoned differently. How could 

 the functional state of the organism be changed, and how, 

 therefore, could adaptation be called forth by any factor of 

 the medium which had not yet entered the organism, but 

 was only about to enter it ? Not at all therefore is such a 

 regulation to be expected as we have sketched ; if there is 

 to be any adaptation to poisons, it only can occur after the 



