ON THE FUNCTIONS OF THE CEREBRUM 315 



logical aspect, therefore, the assumption that animals like the mole 

 possess any special areas of association, however small, appears to be 

 unjustified, and there is also, in view of the following remarks, some 

 reason for believing that such areas are in them physiologically unneces- 

 sary, in spite of the probable requirement by these animals of some 

 physical basis for simple sensory association. 



" Dr. Bolton has suggested to the writer that in the mole and 

 similar animals the fusion zone for simple sensory impressions, 

 i.e. lowest grade of conscious association, lies in the area which has 

 been designated ' motor.' Taking the mole, for example, the areas 

 mapped out as kintesthetic, fifth sensory, visual, &c., are simple sensory 

 reception spheres for the respective senses, whilst urea 1 " (motor) 

 " is the psychic equivalent of all these, and at the same time efferent. 

 Area 1 " (motor) " would thus receive impulses from each or all of the 

 sensory projection spheres and turn them into motor equivalents. 

 It is a general area of simple sensory association with the origin of 

 the efferent (motor) tracts included. This is as far as such an animal 

 as the mole has got in the direction of higher association. J'he struc- 

 ture of the cortex, however, even of this area, especially if regarded 

 as being of an associational type, is of a relatively elementary nature. 



" The above suggestion does away with the apparent anomaly of 

 the relatively great extent of area 1 " (motor) " if this be looked upon 

 as nothing more than a ; Betz cell ' region. It also coincides with 

 the fact that this area ranks with the best developed portion of the 

 cortex as regards supra-granular (pyramidal) layer which mammals 

 such as the mole possess, poor though this is. 



" The writer's views have been founded upon a study of the cortex 

 cerebri, not only in adult mammals but also in foetal and young animals. 

 He concludes that in the cerebral cortex of many and probably of 

 all adult lower mammals there are areas, considerable in extent, which 

 throughout life advance little as regards complexity of their com- 

 ponent nerve cells beyond their condition in the foetal or very young 

 animal. It is therefore on histological grounds presumed that such 

 areas are of comparatively little functional value to the animal. 



" He also considers it proved, as the result of the investigations 

 of Bolton and himself, that the structure of the neopallium is founded 

 upon an infra-granular basis. Further, it is suggested that in the 

 earliest attempts at evolution of structure which come to be of any 

 considerable functional value, the neopallium follows the plan of cor- 

 tical architecture long previously in the phylogenetic scale laid down 

 in the hippocampus, which plan in the latter situation has become 

 fixed, and, as a plan, permanent. The earliest and lowest grade of 



