348 NERVOUS SYSTEM OF VERTEBRATES. 



the olfactory pathways and earlier than the last group of somaes- 

 thetic fibers. 



3. The auditory area. This area on the lateral surface of 

 the temporal lobe close to the island of Reil is better defined than 

 most other areas, since its cortex is much thicker than that of the 

 immediately adjacent regions. Its afferent fibers are myelinated 

 soon after those of the visual field. 



4. The gustatory area. As already suggested in the previous 

 chapter, the gustatory center is closely related to the olfactory. 

 Injury to the cortex or fiber tracts close to the splenium of the 

 corpus callosum in one hemisphere leads to loss of taste on the 

 opposite half of the tongue. Whether the taste center is located 

 in this area of the cortex (area 6 of Flechsig's figures) which is 

 continuous with the subiculum cornu Ammonis, or in the hippo- 

 campus itself is uncertain. When the gustatory connections 

 in lower vertebrates are taken into account it seems very probable 

 that gustatory as well as olfactory sensation is provided for in 

 the archipallium and that both come into relation with the mechan- 

 ism for conscious and voluntary actions only through the asso- 

 ciation centers. 



5. The motor area. This is practically co-extensive with the 

 somaesthetic area. In this area the pyramidal cells reach a 

 greater development than elsewhere and the large pyramids are 

 especially numerous. In those areas in which arise fibers which 

 run to the lower part of the spinal cord many of the pyramidal 

 cells are of gigantic size (e.g. the giant cells of the lobulus para- 

 centralis, the center for the lower limb). The motor fibers always 

 develop myelin later than the sensory fibers of the corresponding 

 area. From the whole motor area arise fibers which descend 

 through the internal capsule and cerebral peduncle and continue 

 through the pons and medulla oblongata into the spinal cord. 

 In the internal capsule they make up the knee and two-thirds 

 of the posterior limb and they constitute about three-fifths of 

 the cerebral peduncle. In the base of the midbrain and pons 

 many of the fibers terminate in relation with the motor neurones 

 of the III, IV, V, VI and VII nerves, most of them crossing to 

 end in the nuclei of the opposite side. Many fibers end also 



