FUNCTIONS OF THE ENCEPHALON. 211 



the discovery that imperfections of speech, constituting a 

 condition called aphasia, arise from disease of a limited por- 

 tion of the brain, immediately outside the island of Reil, 

 particularly on the left side. In these cases the affections of 

 speech are very various, but always depend on mental defi- 

 ciency and not on paralysis of the tongue. In some instances 

 there is total dumbness, in others, incapability of clearly 

 uttering any word; and in a larger number of cases, certain 

 words and phrases are pronounced perfectly, but they are 

 not the words which convey the idea which the patient 

 wishes to express. Perhaps some word is repeated on all 

 occasions; and even when the right expression is suggested 

 to the patient, he is unable to employ any other than that 

 which he keeps repeating, although quite conscious of his 

 blunder. The very variety, Lowever, of these cases of 

 aphasia, shows that they do not arise from damage to the 

 organ of a specific faculty. It is more rational to recognise 

 in them the result of a lesion which interferes with the 

 consentaneous action of the different parts of the hemisphere, 

 by attacking the fibres where they emerge from the corpus 

 striatum to proceed to every part. And we may well believe 

 that consentaneous action of the hemispheres is especially 

 required in so complex a process as conversation, which 

 requires a number of 'distinct mental operations to be carried 

 on at one time. 



155. A consideration of the different mental operations re- 

 quired in talking, is exceedingly instructive. The attention 

 of the speaker is directed principally to the idea which he 

 wishes to express. And, if engaged in a continuous dis- 

 course, he must at the same time think of the sequence of his 

 utterances, and especially what is immediately to succeed the 

 sentence with which he is engaged. The choice of words 

 will also occupy his mind to a recognisable degree; but apart 

 from this intentional choice, there is the choice of the simpler 

 grammar and names of objects, which are so habitual that 

 we fail to separate them in our thoughts from the ideas 

 which they express. Still less attention is devoted to the 

 complex movements of the organs of voice and speech; 

 although they are all performed in the service of the mind, 

 and it was with mental effort in infancy that we learned, by 



