THE CEREBRUM AND HUMAN DEVELOPMENT 147 



in the left handed the balance is reversed : the right hemi- 

 sphere is the dominant one. The most interesting claims 

 made in support of such views have reference to the repre- 

 sentation of language in the human brain. 



The brain of an illiterate man is organized in such a way 

 that oral expression of thought is possible and that the 

 speech of others is comprehended. The educated man 

 has, in addition, an equipment that makes possible the 

 expression of thought in writing and its appreciation 

 through reading. The answering of a question is an act 

 of the reflex type, but one which requires for its execution 

 the fullest development of brain paths. The manner of 

 its accomplishment must depend upon innumerable past 

 events. The destruction of certain connections might be 

 expected to render it impossible to reply to the question. 

 This is a state of things quite often realized. Brain disease 

 is often signalized by disorders in the field of language. 

 Such disorders are not sharply distinguished one from 

 another, but the attempt is often made to classify them 

 under several heads. In general, it may be said that the 

 power to understand and to reproduce language is asso- 

 ciated with connections made through the cortex of the 

 left hemisphere excepting in left-handed subjects. 



Long ago it was noted that in cases where there had been 

 loss of intelligent speech during life a certain limited area 

 in the left frontal region was often found abnormal on 

 postmortem examination. This area became known as 

 the speech center, and the interference with speech re- 

 sulting from its impairment was named motor aphasia. 

 The reputed center is probably a place within which many 

 of the arcs which are necessary for vocal expression of ideas 

 are brought close together. Motor aphasia is not an 

 actual paralysis of the muscle groups required for speech. 

 The use of the same parts for other purposes, such as 

 swallowing, coughing, and even for voice production, 

 when this is not strictly intelligent, may remain quite 

 unimpaired. 



The distinction between the intelligent and the merely 



