(N THE FUNCTIONS OF THE CEREBRUM 313 



latter opinion is, however, disputed in toto by Marie, who has been 

 confirmed in his observations by numerous recent writers. 



Premising, however, that the posterior centres of association 

 were concerned with processes of lower association alone, general 

 mental disability would still be evident in cases of gross lesion of 

 the hinder part of the hemispheres, as the patient would under 

 these circumstances be unable in many cases to produce satis- 

 factory evidence of general mental soundness. In many other 

 cases, also, such an entire disturbance of perceptive and ideational 

 processes as occurs, would be not unlikely to cause too great a 

 strain on the higher associational functions, and to directly result 

 in the development of symptoms of true mental alienation. This 

 is the result which actually ensues in many cases of sense depriva- 

 tion. It is further rendered probable by the fact that no less 

 than one in every 280 of the general population is at the present 

 time suffering from mental alienation, and that the proportion of 

 potential psychopaths is very much greater. That this explana- 

 tion is correct is finally shown by the fact that the latest developed 

 and most complex portion of the human cerebrum, namely, the 

 pref rental area, is, as has already been indicated, the region which 

 is especially affected in the subjects of mental disease. 



Though it is not necessary to describe in detail the differences 

 in degree of development and in structure which exist between 

 the cerebrum of man and those of the anthropoid primates, it is 

 desirable, in this connection, to indicate here briefly the chief of 

 these. It consists, as may be seen by a study of the various 

 publications already indicated, in the immense development of the 

 anterior and posterior zones of association which has occurred in 

 the human brain. Concurrently with this increase in the extent 

 of the great zones of association there has developed in man the 

 power of abstract thought and the employment for this purpose 

 of highly complex articulate and written language. As the centres 

 of lower association in the anthropoid primates differ from those 

 of man in extent and complexity, so do the precepts of the former 

 differ from the highly complex lower psychic units of the latter. 

 Equally does the rudimentary prefrontal region of the anthropoid 

 primates, which imperfectly marshals the relatively simple lower 

 psychic units of these animals, differ from the notable and still 

 developing prefrontal lobe of man, the capacity of which, for 

 co-ordinating the infinitely complex lower psychic units, which 



