EXTRACT XXIX. 



ON THE PSYCHIC OR MENTAL BRAIN CELLS. 



THE psychic or mental neurons, as we have said, constitute 

 the peculiar habitat of the mind, and, in the waking state, 

 are ever engaged, more or less, actively in the performance 

 of what constitutes mental work, conscious and sub-con- 

 scious, the latter resembling reflex action in the domain of 

 neuro-muscular activity. 



Mental cerebration occupies, on a rough estimate, two- 

 thirds of a human lifetime and must, therefore, have, for 

 the material accommodation of its neuronal machinery, a 

 proportionate area of grey matter and correspondingly 

 great dynamic facilities. Both these desiderata are, we 

 think, abundantly supplied by the unclaimed areas of grey 

 matter, or those not yet appropriated by the exponents of 

 cerebral functional localisation, and, indeed, it may be 

 assumed that mental neurons must be in immediate 

 contiguity, if not continuity, with all the cerebral areas 

 in which non-mental function is localised. We, therefore, 

 would claim that the greatest proportion of the grey 

 matter of the cerebrum is engaged in the work of mental 

 cerebration and that " linked up " to it are the areas to 

 which definite neuro-dynamic functions have been assigned. 

 Be this as it may, however, the enormous areas quite 

 untouched by the claims of localisation give to the 

 requirements of psychic activity just that range of choice, 

 so to speak, and that wealth of immediate availability 

 which its supreme importance in the neuro-dynamic work 

 of the organism requires and demands. 



What position the psychic neurons occupy locally in 



