SENSE AREAS AND ASSOCIATION AREAS. 217 



The essential truth of Boiiillaud's observations was estabhshed 

 by other observers, and Broca located the part of the brain in- 

 volved in these lesions in the posterior part of the third or inferior 

 frontal convolution. He described conditions of pure motor 

 aphasia, designated by him as aphemia, which he thought were due 

 to lesions in this gyrus. This region is, therefore, frequently 

 known as Broca's convolution or Broca's center. Subsequent ob- 

 servations have tended to confirm this localization, and what 

 is designated as the " speech center " has been placed in the 

 inferior frontal convolution in the gyrus surrounding the anterior 

 or ascending limb of the lateral fissure (fissure of Sylvius, S, 

 Fig. 97). Many authors insist that this localization is too hmited, 

 and that defects in the power of speech may result not only from 

 injuries to this region, but also from lesions of contiguous areas, 

 including the anterior portion of the island of Reil and the oper- 

 cular portion 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 hemipshere, 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 

 cortical 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 mechanism 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 



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

 Consult for older literature. 



