PHYSIOLOGY OF CONSCIOUSNESS 235 



and cerebral state, easily distinguished from a purely 

 "intellectual" state, which is a cortical process not going 

 on over ancient instinctive paths, but over the pyramidal 

 tract, through the cells of Betz, without as a rule any 

 vaso-motor disturbances. Such disturbances, however, 

 often follow upon intellectual discovery as the results 

 of attainment and, to speak in terms of energetics, of 

 energy suddenly freed. Kepler's emotion on being " freed " 

 by his great discovery is a good example. 



However little such an analysis may commend itself 

 to the more ancient psychologist who lives in a world 

 of words, it is certain that it is only upon such lines that 

 scientific explanation can proceed. It enables the physio- 

 logist to do work without being confused by the necessity 

 of defining terms relative to consciousness about which 

 no two philosophers are at one. So far as science is 

 concerned it may be taken for granted that cerebral re- 

 sponse to the internal and external environment, acting 

 reflexly to excitation and inhibition, is not correlated 

 with consciousness, but is actually consciousness itself, 

 including the subconscious and unconscious : the sub- 

 conscious being tracts in nervous tone which may easily 

 discharge themselves in motor reactions at any time if 

 normally stimulated, while the unconscious consists of 

 other tracts only resulting directly in motor reactions 

 under abnormal excitation or pathological conditions. 



