ON THE FUNCTIONS OF THE CEREBRUM 327 



of written or spoken language for the evolution and reproduction 

 of the highest psychic products, e.g. the production of an abstruse 

 thesis, the language mechanism is made use of solely for the pur- 

 pose for which it has been evolved, namely, as the instrument, 

 and the important assistant, of thought. 



During the above observations an endeavour has been made 

 to indicate that language, though so commonly employed in a 

 largely automatic manner, and with but a feeble appreciation of 

 its signification, is nevertheless in essence a symbolic mechanism 

 for the integration of sensori-memorial images, and, though more 

 complex, is analogous, as an instrument, to the symbolic system 

 employed by mathematicians. 



By its use it is the servant, and the necessary servant, of 

 thought ; by its abuse it becomes the compeer, or even the sup- 

 planter, of thought. 



It is evident from the above considerations thari any gross 

 structural or functional derangement of the language mechanism 

 must necessarily seriously impede, or even in certain cases pre- 

 vent, the adequate performance of those complex processes of 

 association which serve as the physical basis of the psychic 

 functions. 



Apart from its general bearing on the higher functions of the 

 cerebrum, this discussion of the language mechanism has served a 

 further purpose, namely, the paving of the way to a clear under- 

 standing of the far-reaching importance of the investigations of 

 Marie on the subject of aphasia. 



With the latter object in view, another allied subject will now 

 be considered, namely, the gross modifications of cerebral function 

 which are the necessary consequences of congenital or acquired 

 deprivation of the senses of hearing and sight. In cases of sense 

 deprivation, the structural and functional maiming of the cerebrum 

 concerns one or more of its earliest developed, most stable, and 

 functionally lowest parts, namely, the centres of projection. Such 

 lesions consequently present a simpler problem for study, in spite 

 of their far-reaching influence on the functions of the cerebrum, 

 than do the variable and often diffuse lesions which produce the 

 complex symptomatology of aphasia. 



The senses of sight and hearing, especially the latter in un- 

 educated individuals, are so necessary to, and play such an im- 

 portant part in, both the evolution and the conservation of the 



