I. THE THEORY OF MEMORY 343 



the protoplasm structure is converted to III. Thus, both forms, A 

 and B, possess each specific structure. If the protein acquires Ill- 

 structure B-form becomes the normal state of the protein, so that the 

 return to A-form becomes difficult, that is, when the protein stays for 

 a prolonged time at B-form it will forget A-form. 



The newly production of the rearranged side chains in the protein 

 left long under a new environment must be the result of the rear- 

 rangement of polar groups so as to become adaptive to the new form. 

 The same rearrangement of polar groups will take place when the 

 protoplasm is affected by a virus, in response to whose structure the 

 polar groups of the protoplasm protein are rearranged. Such adaptive 

 rearrangement of the structure appears to be a common character of 

 proteins, but the character is never peculiar to proteins, since similar 

 adaptation to a new environment can occur with usual elastic sub- 

 stances other than protein. A piece of elastic thread, for instance, 

 whether it is composed of protein or steel, after standing in A-form 

 for a prolonged period can be changed to B-form only with difficulty 

 at first, but the repetition of the change will make the change easy 

 and a long maintenance of the B-form will render the form normal, 

 the return to the original form becoming difficult. Also in such a 

 case, the adaptation may occur owing to the modification of the inner 

 structure of the thread to adapt itself to the new form. 



3. The Cause of Aging 



It has been known for a long time that generally colloids includ- 

 ing proteins grow old like livings. In the opinion of the writer, the 

 process of just considered adaptation of the protein to environments 

 leads in the long run to aging. During the adaptation process the 

 fixation of the inner structures may be advanced so far that the forms 

 of the protein m.olecules become hardly changeable to other forms. 

 Such a hardening of the structure is considered to be aging. 



We shall consider in detail of this phenomenon with Fig 33. Now 

 it is assumed that a polypepide chain can take two forms, a and h, 

 according to the environment, A and B, under which it stands. If 

 the protein is left for a prolonged period under the same condition, 

 the inner structure will gradually be fixed by the rearrangement or 

 the shift of polar forces, until it attains the forms «i or h^. The pro- 

 tein in such a form is in a well adapted state so that the change from 

 one form to the other will be brought about only with difficulty, but 

 if the change is repeatedly raised by the repetition of environmental 

 change, the arrangement of the polar forces which may hinder the 



