THE CEREBRUM 269 



be facial, brachial, crural, brachio-facial monoplegia, etc. There 

 can be no doubt that from the motor cortical zone pass the fibers 

 which constitute the pyramidal tracts of the cord. 



Sensory Centers. Centers for the reception of impressions 

 giving rise to general sensation may exist. Fibers from the tem- 

 poro-sphenoidal and occipital lobes pass through the posterior 

 third of the posterior division of the internal capsule, and it may, 

 therefore, be assumed that these parts of the cerebrum are con- 

 nected with general sensation. 



Special Centers. Besides these areas for motion and general 

 sensation, special centers certainly exist. 



The Optic Center is in the occipital lobe, probably in the cuneus. 

 Removal of the right occipital lobe is followed by lefthemiopia 

 and vice versa; removal of both causes total blindness. 



The Olfactory Center is probably on the inner surface of the 

 anterior extremity of the uncinate gyms (inner extremity of the 

 temporal lobe) . 



The Gustatory Center is supposed to be in the temporal lobe 

 very near the preceding. 



The Auditory Center is located in the superior and middle 

 convolutions of the temporo-sphenoidal lobe. 



The Center for Cutaneous Sensations cannot be strictly lim- 

 ited, though it is said to correspond with the motor area. 



The Center for Muscular Sensations is thought to be in the 

 lower parietal region. 



The Speech Center. One may not be able to speak because 

 he cannot control the muscles usually involved in such an act, 

 or because he has no comprehension of the meaning of words, 

 or because he is incapable of forming the idea which links the 

 reception of the impression and the muscular act. Aphasia is 

 the term generally applied to inability to express one's self by 

 language. It is to be distinguished, however, from aphonia, 

 which is simply a loss of voice. Ataxic aphasia is an inability 

 to express ideas only by reason of muscular incoordination; a 



