TASTE CENTER OF THE CORTEX 587 



cells and granular matter. A full description of the anatomy of these parts 

 is given later. 



Fibers of the olfactory nerve proper are found below this layer, and pass 

 through the cribriform plate to be distributed to the olfactory mucous mem- 

 brane. They arise from cells in the olfactory mucous membrane, and end in 

 the glomeruli. The peduncle of the nerve or the olfactory tract, as it is some- 

 times called, is made up of longitudinal fibers originating in the bulb, with 

 neuroglia and some nerve cells. 



The fibers of the olfactory tract have been traced into the nucleus amygdalae 

 and its junction with the hippocampal gyrus in the temporal lobe, figure 399. 

 The hippocampus must be in some way connected with smell, since a lesion of 

 it, leaving the olfactory tract uninjured, seriously interferes with that sense. 



Taste Center of the Cortex. It is very uncertain where the taste 

 center is situated, if such exist. It has been placed in the anterior portion of 

 the inferior temporal convolution, not far from that of smell, figure 399. 



Auditory Center in the Cortex. This center has been localized in 

 the superior temporal convolution. Experiments have been made which 

 connect auditory impulses on either side with the inferior corpus quadrige- 

 minum and the median corpus geniculatum, for when the internal ear is 

 destroyed there results atrophy of these bodies as well as of the lateral 

 fillet of the opposite side. On the other hand, destruction of the part of the 

 temporal lobe above indicated is similarly followed by atrophy of the nuclei 

 of the same side. These nuclei bear much the same relation to the sense 

 of hearing as do the anterior corpora quadrigemina and the lateral corpora 

 geniculata to the sense of sight, figures 389 and 416. 



ASSOCIATION CENTERS OF THE CEREBRAL CORTEX. 



The theory of localization of the function of different parts of the cerebral 

 cortex has received substantial support from the study of the motor and the 

 sensory areas in man and the mammals. But when the exploration of the 

 cortex is complete and the motor and sensory areas are bounded as definitely 

 as may be, there still remain great areas in which stimulation is apparently non- 

 effective so far as our present means of interpretation reveal. Traumatic 

 and pathological lesions produce no sensory or motor disturbances. The 

 areas of this class which are most extensive, i.e., which cover the greatest 

 amount of cortex, are three in number the frontal lobe, the parietal lobe, and 

 a large part of the temporal lobe below the superior temporal convolution. 



Flechsig has made a study of the development of the human brain, paying 

 especial attention to the progressive development of the great tracts of fibers. 

 He has shown that the tracts appear in a certain order of sequence, also that 

 the myelinization takes place progressively. On the assumption that ef- 

 fective functionization is acquired with the myelin sheath, he showed a close 



