SENSE AREAS AND ASSOCIATION AREAS. 207 



however, cannot be rightly placed to his credit, since his reasons for its location 

 were, so far as we know, entirely unjustified. It cannot be reckoned as more 

 than a coincidence that in this particular his phrenological localization was 

 afterward in a measure justified by facts.) 



The essential truth of Bouillaud's observations was established 

 by other observers, and Broca especially located the part of the 

 brain involved in these lesions in the posterior part of the third or 

 inferior frontal convolution. This region is, therefore, frequently 

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

 servations have abundantly 'confirmed this localization, and what 

 is designated as the " speech center" is placed in the inferior frontal 

 convolution in the gyrus surrounding the anterior or ascending 

 limb of the fissure of Sylvius (S, Fig. 91); although many authors 

 insist that this localization is too limited, 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 island 

 of Reil. Autopsies have shown that in right-handed persons 

 the speech center is placed or is functional usually in the left cere- 

 bral hemisphere, while in the case of left-handed individuals 

 aphasia and paralysis are 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 ex- 

 press 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 completeness and 

 in many curious varieties. The individual may retain the power to 

 use a limited number of words, with which he expresses his whole 

 range of ideas, as, for instance, in the case described by Broca,* 

 in which the individual retained for the expression 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. It does not seem to be certain whether or not, in 

 the case of complete lesion of the center on one side, the ability 



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

 Consult for older literature. 



