330 RESEARCHES ON CORTICAL LOCALISATION AND 



In persons who acquire sense deprivation later in fife, the 

 mental stress involved on the one hand in the sense disability, 

 and on the other in the more or less unsuccessful attempts to 

 revive the related memories which tend to pass more and more 

 into the permanently subconscious, or to replace the absence of 

 these memories by the integration of percepts and concepts on 

 an- unusual sensori-memorial basis, often, or perhaps invariably, 

 results in the development of irritability, or depression, or general 

 emotional instability. In rare cases like one cited by Clouston, 

 partial removal of the sense deprivation by operation (for cata- 

 ract) may result in a return to normal psychic life. In the case, 

 however, of individuals who possess higher cortical neurones of 

 deficient durability, insanity followed by dementia ensues. 



It may finally be stated that cases of congenital or early 

 acquired deafness are more liable to imperfect mental development, 

 with which is associated mutism, than are cases of congenital or 

 early acquired blindness. 



Further, both in the cases in which the sense deprivation is 

 congenital or acquired early in life, and in those in which it is 

 acquired after adult life has been reached, cerebral involution is 

 more likely to occur in the case of the deaf than in that of the 

 blind. This statement is supported by a series of cases which 

 were recently published by the writer, for, of the ten in the series, 

 three were deaf and dumb, two were deaf, four were almost or 

 totally deaf and blind, and only one, a well-marked high-grade 

 ament, who had been certified for thirty-seven years, was blind. 



RECENT RESEARCHES ON APHASIA 



The description of the language mechanism and the evidence 

 of its fundamental importance to the performance of the psychic 

 functions especially that derived from the study of cases of 

 sense deprivation have been given at considerable length. Whilst 

 the primary object of the writer has been the elucidation of the 

 manner in which the higher functions of the cerebrum are per- 

 formed, he has at the same time endeavoured to so present the 

 subject of language as to prepare the reader, not merely for the 

 appreciation of the gist of the recent researches on aphasia, but 

 for the acceptance of their results as truths of great importance. 



The statements, that our views* of aphasia require entire re- 



