366 THE ASCENT OF MAN 



meriting with powers and faculties so fresh that 

 heredity in handing them down has been unable 

 to accompany them with full directions as to their 

 use. 



The Brain of Man, to change the figure — if 

 indeed any figure of that marvellous molecular 

 structure can be attempted without seriously mis- 

 leading — is an elevated table-land of stratified ner- 

 vous matter, furrowed by deep and sinuous canons, 

 and traversed by a vast net-work of highways along 

 which Thoughts pass to and fro. The old and 

 often-repeated Thoughts, or mental processes, pass 

 along beaten tracks ; the newer Thoughts have 

 less marked footpaths; the newer still are compelled 

 to construct fresh Thought-routes for themselves. 

 Gradually these become established thoroughfares; 

 but in the increasing traffic and complexity of 

 life, new paths in endless multitudes have to be 

 added, and bye lanes and loops between the older 

 highways must be thrown into the system. The 

 stations upon these roads from which the travellers 

 set out are cells ; the roads are transit fibres ; 

 the travellers themselves are in physiological lan- 

 guage nervous discharges, in psychological language 

 mental processes. Each new mental process in- 

 volves a new redistribution of nervous matter 

 among the cells, a new travelling of nervous dis- 



