THE BRAIN. 



37 



tongue, and platysma myoid muscle, around its lower extremity. The leg, arm, and 

 face centres are, respectively, opposite the posterior extremities of the superior, 

 middle, and inferior frontal convolutions. 



The upper portion of the motor area passes over the upper margin of the hemi- 

 sphere and down on its medial side almost as far as the callosomarginal fissure and 

 paracentral lobule. 



The Sensory Area. The portions of the cerebrum involved in cutaneous 

 and muscular sensibility embrace the posterior portion of the parietal convolutions, 

 the precuneus or quadrate lobule, and gyrus fornicatus as far forward as the motor 

 area on the medial aspect. 



The visual area embraces the occipital lobe, particularly its cuneus lobule, 

 and region of the calcarine fissure on the medial surface of the hemisphere. The 

 anterior portion of the occipital lobe and the region of the angular gyrus are con- 

 Foramen interventriculare 



Commissura medius 



Thalamus 



Commissura posterior 

 Corpus pineale 



Ventriculum lateralis 



Corpus striatum 



Commissura anterior 



Corpora quadrigemina 



Ventriculum tertius 

 Pons 



Ventriculum quartus 

 Medulla 



FIG. 46. Foreshortened view showing corpus striatum, thalamus, corpora quadrigemina, lateral, third, and 



fourth ventricles, etc. 



cerned in the more complex phenomena of sight, and their destruction produces 

 word-blindness. Destruction of the centres on both sides produces what has been 

 called mind-blindness, because objects can no longer be recognized. 



The Auditory Area. The centre for hearing is located in the superior and 

 middle temporosphenoidal convolutions. It requires destruction of these convo- 

 lutions on both sides of the brain to produce total cerebral deafness. The memory 

 or recognition of spoken words (word hearing) is apparently performed by the pos- 

 terior ends of the superior and middle (ist and 2d) temporosphenoidal convolutions. 



Gustatory Area. The sense of taste is supposed to be located on the under 

 and inner surfaces of the temporosphenoidal lobe or fourth temporal convolution. 



Olfactory Area. The sense of smell is supposed to involve the anterior portion 

 of the gyrus fornicatus and the upper medial portion of the temporosphenoidal lobe. 



The cerebral areas for both smell and taste have not been as yet accurately 

 determined. 



FUNCTIONS OF THE BASAL GANGLIA. 



Corpus Striatum and Thalamus. The exact functions of the corpus stria- 

 tum, embracing the caudate and lenticular nuclei, and of the thalamus are not 

 known. They are most often affected in apoplexies ; lesions of the corpus striatum are 

 accompanied by disturbances of motion, and those of the thalamus by disturbances of 

 sensation. 



