S o8 TEXT-BOOK OF PHYSIOLOGY. 



impairment of sensibility." In several cases of excision of the human 

 cortex in the Rolandic region by surgical operations careful studies 

 of the patients failed to show any impairment of sensation. Other 

 competent observers, however, have reported a number of cases in 

 which anesthesia more or less pronounced and persistent has accom- 

 panied lesions of the motor area. The explanation of these contra- 

 dictory observations is not apparent. 



The olfactory area has been assigned to the uncinate convolution, 

 the anterior part of the gyrus fornicatus, and the posterior part of the 

 base of the frontal lobe. Lesions in this region are frequently 

 accompanied by subjective olfactory sensations. 



The gustatory area has been assigned to the fourth temporal 

 convolution. 



The auditory area has been assigned to the posterior portion of 

 the superior temporal convolution and to the retro-insular convolu- 

 tions, the island of Reil. Unilateral destruction of this region is 

 followed by only a partial loss of hearing in the opposite ear (owing 

 to the partial decussation of the cochlear nerve), which, however, 

 may be recovered from after a time, owing probably to a compensatory 

 activity of the insular convolutions. Bilateral disease of this region 

 is followed by complete deafness. Within this area there is a smaller 

 region, disease of which is accompanied by word-deafness only, the 

 patient being unable to distinguish the tone intervals between words 

 and syllables and therefore hearing only confused noises. Object 

 hearing was also a separate area of representation. 



The visual area has been assigned to a triangular shaped area on 

 the mesial surface of the occipital lobe, which includes the gray matter 

 above and below the calcarine fissure (the cuneus and upper part of 

 the lingual lobe), and to the gray matter of the first occipital convo- 

 lution on the lateral aspect of the occipital lobe. Focal lesions of this 

 area on one side are followed by lateral homonymous hemianopsia, 

 which, however, does not involve, as a rule, the fovea or macula. 

 It is, therefore, the area of homonymous half-retinal representation. 

 The location of the area for macular or central vision is uncertain. 

 Henschen locates it in the anterior part of the area near the ex- 

 tremity of the calcarine fissure, and asserts that in each area both 

 maculae are represented. From experiments made on monkeys 

 Schafer locates it in the same region. Beyond the limits of this 

 visual area and on the lateral aspect of the parietal lobe there is a 

 region (the supra-marginal convolution and angular gyrus) in which 

 impressions of words and letters seen have their representation. 

 Destruction of this area by diseases is followed by word- and per- 

 haps letter-blindness, the patient being unable to recognize words 

 and letters seen because of failure to revive the memory images of 

 words and letters. The areas for visual sensations and optic memory 



