788 THE SENSORIAL CORTICAL CENTERS. 



the new-born dog that the contralateral center was less well developed. Destruc- 

 tion of the entire region on both sides causes deafness (with mutism). Ferrier 

 demonstrated the center in apes, rabbits, jackals, and cats. 



According to Luciani the auditory center extends from the temporal lobe to 

 the parietal and frontal lobes, the hippocampal gyrus and the cornu Ammonis. 

 Each ear is in connection with both centers, although most intimately with that 

 of the opposite side. After total extirpation of the auditory center on both 

 sides mind-deafness alone develops. 



Munk and Ferrier locate the olfactory center in the dog in the hippocampal 

 gyrus. After destruction of the center on each side in the ape the sense of smell 

 and that of taste were abolished. The psycho-osmic and psychogeusic centers 

 located in this situation have as yet not been differentiated. According to Luciani 

 the hippocampal gyrus and the cornu Ammonis constitute the olfactory center. 

 Partial decussation is to be assumed also in this case, but the non-decussating 

 bundle is the larger. 



On irritation of this area Luciani observed in apes, dogs, cats, and rabbits 

 distortion of the lips and partial closure of the nasal orifice on the same side. 

 According to Zuckerkandl, who bases his conclusions upon comparative anatomical 

 observations, the cortical portion of the olfactory center is constituted of the 

 central extremity and the frontal extremity of the lobe of the corpus callosum, 

 of the hippocampal lobe together with the uncus, of the cornu Ammonis including 

 the marginal convolution (particularly the dentate fascia), of the cortex of the 

 olfactory peduncle, of the cortex of the anterior perforated lamina and of the 

 olfactory bulb. 



A cortical olfactory center is present among vertebrates first in reptiles, 

 and this is at the same time the earliest psychosensorial organ that appears. It 

 may be concluded from this fact that, phylogenetically, the first psychic, activity 

 in the animal kingdom is concerned with the perception of odors. 



Munk believes that the surface of the brain in the region of the motor 

 centers is at the same time the sensory sphere, that is that it serves also for 

 the reception of tactile, muscular, and innervational impressions from the oppo- 

 site side. The boundaries of the areas for the individual portions of the body 

 in the dog are indicated in Fig. 259. After injury of this region the function 

 mentioned is lost. The sensory sphere in apes is situated in the parietal lobe and 

 each individual area is related to a definite portion of the body. After total 

 extirpation of the arm-area and the leg-area, tactile sensibility is lost perma- 

 nently, while after partial extirpation return of sensibility takes place later. 



Luciani, however, rejects such precise limitation for the individual regions of 

 the body. According to Bechterew the centers in the dog for the perception of 

 tactile impressions, the muscle-sense and sensations of pain are situated in the 

 neighborhood of the motor zone, the first immediately behind and external to 

 the motor area, the others in the region just above the beginning of the fossa of 

 Sylvius. According to Schafer extirpation of the gyrus fornicatus is followed 

 by permanent impairment of sensibility in apes. 



THE CORTICAL THERMIC CENTER. 



DIVERGENT VIEWS AS TO THE LOCALIZATION IN THE CORTEX. 

 OTHER CORTICAL FUNCTIONS. 



A. Eulenburg and Landois succeeded in discovering on the surface 

 of the cerebrum of the dog an area from which an undoubted influence 

 is exerted upon the temperature and the size of the vessels in the con- 

 tralateral extremities. This area (Fig. 258 I, t) comprises in general 

 the region in which at the same time the motor centers for the flexors 

 and the rotators of the foreleg (3) and for the muscles of the hind ex- 

 tremity (4) are situated. The effective areas for the anterior and pos- 

 terior extremities are widely separated from each other. That for the 

 foreleg is situated somewhat further forward, close to the lateral ex- 

 tremity of the cruciate sulcus. Destruction of this region is followed by 

 elevation of the temperature in the contralateral extremities, and this 

 may be variable in degree from 1.5 to 2 or even as much as 13 C. 



