148 COSMIC PHILOSOPHY. [pi il 



The correspondence between the subjective and the objec- 

 tive sides of the phenomena is thus complete, and the in- 

 creasing complication of cell and fibre in the brain, from 

 infancy to old age, is seen to have a psychological meaning. 

 If the acquisition of a new idea is attended by the passage 

 of a wave of molecular motion along a new path ; and if 

 recollection is a state of consciousness attending the trans- 

 mission of a later wave along the same path ; we have an 

 adequate physical interpretation of the fact that the repeti- 

 tion of an idea is favourable to the recollection of it. And 

 we have also the physical interpretation of habit and pre- 

 judice. Molecular motions that have been repeatedly trans- 

 mitted between particular groups of nerve-cells, end by 

 establishing more or less intricate webs of transit-lines 

 which cannot be obliterated. No effort can prevent their 

 occasional recurrence along these lines, or establish a new 

 plexus of transit-lines, involving the derangement of the old 

 ones. Late in life, when the ratio of repair to waste is 

 greatly diminished, when the nutrition of the cerebral tissue 

 is impaired, when the pulling to pieces and putting together 

 of molecular clusters in which nutrition consists goes on 

 slowly, then the formation of new sets of transit-lines be- 

 comes especially difficult ; and hence, as we say, the shaking 

 off of old habits and prejudices, and the acquiring of new 

 and strange ideas, is next to impossible. It is proverbially 

 hard to teach an old dog new tricks. We may here also see 

 why it is impossible to learn or to carry on complicated think- 

 ing when in a state of anamia : the nutritive changes go on 

 too slowly. Changes in memory further illustrate the theory. 

 In youth, when the excess of repair over waste is at the 

 maximum, but few discharges through any transit-fibre are 

 needful in order to work a permanent nutritive change, set- 

 ting up a line of communication which shall last through 

 life : hence learning is easy and rapid, and memory is power- 

 ful. In old age, when waste is slightly in excess of repair, 



