178 THE CEREBRUM. 



(Rolandi), though eye movements appear to be represented in 

 the posterior end of the middle frontal gyrus; the arm area com- 

 prises the region between the genu inferius and the genu superius, 

 the thumb, ringers, wrist, fore-arm, arm and shoulder move- 

 ments being represented in this ascending order; just above the 

 shoulder area, at the genu superius, is the trunk area; and above 

 that, in the anterior central gyrus and in the paracentral lobule, 

 in front of the sulcus centralis, is the center for leg movements, 

 The representation in the leg center is inverted, the ascending 

 order being hip, thigh, leg, ankle, toes and great toe. 



The psychic motor areas, or areas for educated movements 

 are located just anterior to the above motor areas, in the anterior 

 central gyrus and in the contiguous ends of the superior, middle 

 and inferior frontal gyri (Figs. 54 and 55). These areas are 

 believed to send their axones to the emissive motor centers in the 

 cortex. The psychic motor center for the lower extremity is 

 probably located just in front of its emissive motor center in the 

 anterior central and superior frontal gyri. In the posterior end 

 of the middle frontal gyrus is the psychic motor center for the 

 arm, the writing center of Gordinier; and in the inferior frontal 

 gyrus the center for the organs of voice and speech, hence the 

 motor speech center. In right handed people these centers are 

 developed only in the left cerebral hemisphere. 



Common Sensory Area (Figs. 54 and 55). According to Dr. 

 Alfred W. Campbell the receptive area of common sensation is 

 limited to the posterior wall of the sulcus centralis, including 

 the anterior one-half of the posterior central gyrus and that part 

 of the paracentral lobule which is continuous with it. This area 

 undergoes exclusive Nissl degeneration in locomotor ataxia 

 (Campbell). It is probably divided into segments similar to 

 those of the motor area (Spiller). 



Psychic Sensory Area (Figs. 54, 55, 56 and 57). A large portion 

 of the remainder of the parietal cortex probably constitutes a 

 number of centers for the interpretation of common sensory 

 impulses, hence the term, psychic sensor)' area. Impressions 

 of the muscular sense are believed to be interpreted in the supra- 

 marginal gyrus and the center of stereognosis is said to be located 



