ON THE FUNCTIONS OF THE CEREBRUM 309 



is given so differently by Brodmann and by Campbell that it 

 might appear that no advance had been made on his original 

 description. A careful study of the maps of Brodmann and of 

 Campbell in the light of the writer's special knowledge of the 

 histological characters of several portions of the cortex cerebri has, 

 however, convinced him that the more elaborately detailed map 

 of the former of these investigators is the more correct. In support 

 of this statement he would refer to the recent paper of Gordon 

 Holmes on the histology of the post-central gyrus, in which the 

 findings of Brodmann are confirmed. ^ 



The writer is, however, of the opinion that, whilst further histo- 

 logical research will undoubtedly enable certain other projection 

 areas to be as precisely defined as have been the psychomotor 

 and visuo-sensory areas (even if Brodmann's findings in those 

 respects should not be confirmed in their entirety), the exact 

 differentiation of the remainder and greater portion of the grey 

 mantle into equally precise areas will be attended with great 

 difficulty owing to the probability that considerable differences 

 exist in the case of different individuals. He nevertheless regards 

 such precise differentiation as possible, and considers that light 

 will in the future be thrown on the histo-pathology of amentia or 

 cerebral sub-evolution by this means. For example, in the six 

 occipital regions mapped out by the writer in the paper already 

 referred to, the shape and apparent extent of the visuo-sensory 

 area exhibit considerable individual differences quite apart from 

 the questions of age and blindness. As such differences exist in 

 a projection area, it is probable that more marked variations will 

 occur in the case of the later specialised areas of different brains. 

 Though fissuration and histological differentiation do not run hand 

 in hand, the researches of Karplus on the fissuration of the human 

 cerebrum with regard to family likeness are worthy of mention in 

 this connection. 



Beyond a relatively gross subdivision of the cerebral cortex 

 into different areas, it is unlikely that the histological method 

 will be of assistance, as cerebral function, even when relatively 

 low in grade, consists of associational processes which involve 

 many related regions of the cortex. Further, as is shown espe- 

 cially by the study of sense deprivation, the maimed brains of 

 patients suffering from this disability are capable, to a remarkable 

 extent, of replacing the normal methods of association by dis- 



