220 PHYSIOLOGY OF CENTRAL NERVOUS SYSTEM. 



including the anterior portion of the island and the opercular por- 

 tion of the central convolution. Autopsies have shown that in 

 right-handed persons the speech center is placed or is functional 

 usually in the left cerebral hemisphere, while, on the other hand, it 

 is stated, although hardly demonstrated, that in the case of left- 

 handed individuals aphasia is produced by lesions involving 

 the right side of the brain. This region is not the direct cor- 

 tical motor center for the muscles of speech. It is possible that 

 aphasia may exist without paralysis of these latter muscles. It is 

 rather the memory center of the motor innervations necessary to 

 form the appropriate sounds or words with which we have learned 

 to express certain concepts. The child is taught to express certain 

 ideas by definite words, and the memory apparatus through which 

 these associations are transmitted to the motor apparatus may be 

 conceived as located in the speech center. Lesions of any kind 

 affecting this area will, therefore, destroy more or less the ability 

 to use appropriately spoken words, and clinical experience shows 

 that motor aphasia may be exhibited in all degrees of complete- 

 ness and in many curious varieties. The individual may retain 

 the power to use a limited number of words, with which he ex- 

 presses his whole range of ideas, as, for instance, in the case de- 

 scribed by Broca,* in which the individual retained for the ex- 

 pression of numbers only the word " three," and was obliged to 

 make this word do duty for all numerical concepts. Other cases 

 are recorded in which the patient had lost only the power to use 

 names that is, nouns (" Marie ") or could remember only the 

 initial letters. Others still, in which words could be used only 

 when associated with musical memories, as in singing; or in which 

 the words were misused or employed in wrong combinations 

 (paraphasia) . Motor aphasias have been classified in various 

 ways to suit the different schemata which have been invented to 

 explain the cerebral mechanism of speech, but the whole subject 

 is in reality so complex that most of these classifications must be 

 received with caution. There seems to be no doubt, however, that 

 a condition of what may be called pure motor aphasia may result 

 from localized injuries to the brain. In this condition there is 

 loss of the power of articulate speech, without paralysis of the 

 muscles of articulation, and with the preservation of what has been 

 called internal language, that is, the power to conceive the ideas for 

 which the appropriate verbal expressions are missing. Most 

 authors conclude that this condition is due to an injury or lesion in 

 Broca's convolution, but others contend that the evidence for 



* Exner, "Hermann's Handbuch der Physiologie," vol. iii, part u, p. 342. 

 Consult for older literature. 



