THE SENSORY CORTICAL AREAS 653 



on animals it appears that the cortical area of the general sensory and tactile 

 nerves is very closely related to the motor cortical field in a spatial sense 

 as well as in a functional sense, but that in man it lies, at least for the most 

 part, outside the motor cortical field (Fig. 293). 



B. THE CORTICAL AREAS OF TASTE AND SMELL 



The parts of the brain directly connected with the olfactory organ are very 

 differently developed in different genera of animals. In man, as we have already 

 seen (page 486), this sense is but slightly developed. 



Our knowledge of the cortical areas of the olfactory nerves is based almost 

 exclusively on anatomical evidence. Judging by this, the olfactory area in 

 man embraces the whole posterior edge of the base of the frontal lobe and 

 the basal part of the gyrus fornicatus on the one hand and the uncus and a 

 part of the neighboring inner apex of the temporal lobe on the other. These 

 two areas are connected at the base of the insula (Fig. 294). 



Speaking of the cortical area for the gustatory nerve, Bechterew states 

 that in the dog bilateral destruction of a region corresponding to the anterior 

 lower portion of the third and fourth external convolutions (Fig. 282) oblit- 

 erates the sense of taste entirely; with unilateral destruction there is total 

 loss of taste on the opposite side and a slight weakening on the same side 

 as the lesion. Following only slight injuries, an improvement is noticeable 

 within a few days, while after more extensive lesions the defect continues for 

 months. Stimulating these portions of the cortex, Bechterew noted contrac- 

 tion of the lips on the opposite side, movements of the tongue, movements 

 of mastication and swallowing. 



C. THE AUDITORY AREA 



H. Munk finds that removal of the temporal lobes on both sides produces 

 complete deafness, but no other disturbance. Extirpation of one temporal 

 lobe makes the animal deaf in the opposite ear. Stimulation of the temporal 

 convolutions produces movements of the external ear which are probably con- 

 nected in some way with auditory impressions. 



Similar results have been observed by other authors, but we find it stated by 

 still others that bilateral extirpation of these parts produces only temporary deaf- 

 ness or no evident sign of it at all. Brown and Schafer completely removed both 

 temporal lobes from a monkey. Immediately after the operation the animal's 

 intelligence was very much affected, but this condition gradually passed away so 

 that the animal once more became very intelligent. The authors themselves and 

 several other physiologists and physicians tried numerous experiments with the 

 animal and came to the conclusion that all its senses including hearing were per- 

 fectly acute. Moreover, there was no chance for the claim that the reactions of 

 this animal to auditory stimuli were really due to excitation of the cutaneous 

 nerves. From these observations it appears therefore that the auditory pathways 

 do not end in the temporal lobes alone, although they may be most concentrated 

 there. 



The course of the fibers of the cochlear nerve inside the cerebrum leaves 

 no doubt that the temporal lobes in man stand in very intimate relation with 



