ON THE FUNCTIONS OF THE CEREBRUM 311 



are chiefly concerned with the reception of afferent impressions of 

 various kinds, and that the cortex in relation to each of these is 

 especially concerned with associational functions or psychic pro- 

 cesses hall -marked by their several sensory areas. It may further 

 be provisionally stated that a large part of the remainder of the 

 cortex under consideration may probably be regarded as the 

 physical basis of language (not words, but word-groupings), i.e. a 

 mechanism for the symbolic integration of the various more or 

 less complex products of cerebral association. This question will 

 be considered later in connection with the subject of the higher 

 functions of the human cerebrum. 



As regards the frontal lobes, but two regions call for especial 

 remark here, namely, the psychomotor area and the prefrontal 

 region. 



With regard to the psychomotor area (" precentral " of Campbell, 

 4 of Brodmann), it is hardly necessary at the present time to 

 indicate the various reasons which prove that this area is asso- 

 ciational and not sensory in function, and that, in addition, it 

 possesses a direct efferent connection with the motor groups of 

 lower neurones. 



The cerebral cortex may, in fact, be regarded as a complex 

 sensori-motor mechanism. Of this the non-frontal portion consists 

 of sensory areas (centres of projection) and of zones of association 

 of various types and grades of complexity. The frontal lobes, on 

 the other hand, contain the efferent portion of the mechanism. 

 The psychomotor area may be regarded as the lowest grade of 

 this, and as concerned on the one hand with the integration 

 and on the other with the efferent transmission of the motor 

 expression of the associationally elaborated results of sensorial 

 stimulation. 



The prefrontal region (10 of Brqdmann) is the most complex 

 of the zones of association of Flechsig. It is the last portion of 

 the cortex to be evolved and the first to undergo retrogression. 

 The outer cell lamina or pyramidal layer of this region varies 

 directly in depth according to the mental power of the individual, 

 in the case of foetuses and infants, idiots and imbeciles, and chronic 

 and recurrent lunatics without dementia. In cases of dementia, 

 degrees of retrogression occur which vary directly with the existing 

 grade of dementia. Finally this layer of the cortex is the only 

 layer which varies measurably in depth in normal individuals. On 



