THE PSYCHIC BRAIN CELLS 327 



relationship to the sensory and motor neurons it is 

 impossible to say, so far as observation and experiment 

 up to now warrant any statement on the subject. It 

 must of necessity be, however, that the cerebral neuronal 

 commonwealth is so layered, or intermixed, that the 

 linkage of the sensory, or afferent, and the motor, or 

 efferent, with the psychic neurons is so intimate and 

 direct as to require direct or continuous but insulatable 

 and breakable histological continuity, and functional inter- 

 dependence and oneness. 



Viewed thus it becomes apparent that both the afferent 

 and efferent, or sensory and motor, neurons, when long 

 in active functional employment, become exhausted and 

 require uncoupling from the psychic neurons, and that 

 these latter likewise require rest, and so, when one psychic 

 neuronal area has become exhausted from too prolonged use, 

 another, or other, fresh areas can be called upon to take 

 up the work of psychic cerebration until such time as the 

 fatigued neurons have sufficiently recovered their psychic 

 tone so as to be able to resume the work of active psychic 

 cerebration. If it is consistent with universal experience 

 that psychic cerebration is most effective, and successful, 

 when freed from the necessity of attending to the calls of 

 afferent and efferent, or sensory and motor, innervation, 

 it follows that the periods of awaking from sound sleep, 

 and before the sensory and motor neurons have had time 

 to disturb the flow of psychic cerebration, and when the 

 sensory and motor neurons have been completely inhibited 

 from the psychic, coincide with the periods of most suc- 

 cessful psychic cerebration, or intellectual exercise. 



These views, histologically regarded, are consequently 

 consistent with the ideas that the three forms of neurons, 

 viz. the psychic, or mental, the sensory, and the motor, 

 are each, and all, locally present, in a greater or lesser 

 extent, in every section of cortical space and contained 

 neurons within any and every area of the cerebral grey 

 matter, and that the histological requirements of the 

 doctrine of cerebral functional localisation do not preclude 

 the existence in juxtaposition of all three forms of neurons. 

 We may, therefore, take it that within the entire area of 

 the grey matter of the cerebrum we have to deal with a 



