THE CEREBRUM 599 



or perhaps to a compensatory activity of the primary area of the same side, 

 now excited to activity by the fibers which did not decussate, but which 

 ascended directly to the primary area. Bilateral destruction of this region 

 is followed by complete deafness. The primary area is connected on the 

 one hand with the basal auditory center (the internal geniculate body) 

 by the auditory radiation, and on the other hand with the secondary 

 areas by association fibers. 



In the first of these secondary areas there are cells in which the sounds 

 of objects are registered (object hearing) ; in the second of these secondary 

 areas there are cells in which the sounds of words, letters, etc., 

 are registered or memorized. If these areas are destroyed by disease 

 the condition of object-deafness and word-deafness is established. If 

 word-deafness alone exists, the patient though able to recognize sounds 

 is unable to understand spoken language and is in the condition of a man 

 who is hearing a language of which he has not the slightest knowledge. 

 The same holds true for the perception of sensations of sound produced 

 by objects. 



The afferent pathway by which nerve impulses, developed in the terminal 

 portions of the auditory nerve by the impact of atmospheric vibrations are 

 transmitted to the auditory area, is considered in connection with the con- 

 sideration of the auditory nerve and tracts. 



In the temporal lobe there are other areas, some of which are more or 

 less associated with the auditory nerve, such as intonation, equilibratory 

 and orientation areas. In the subtemporal and probably in the medi- 

 temporal convolution as well, there is an area in which, it is believed by 

 some clinicians, words are associated with concrete ideas of objects recog- 

 nized by one or more of the senses. To this area the term naming area 

 has been given. It is connected by association fibers with the areas for 

 word hearing and word seeing. 



7. The Visual Area. The area for visual sensibility has been assigned to 

 portions of the occipital and parietal lobes and may be divided into 

 primary and secondary areas. 



The primary area is located in a triangular-shaped area on the mesial 

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

 the parieto-occipital and the calcarine fissures (the cuneus), and in 

 the gray matter of the first occipital convolution on the lateral aspect 

 of the occipital lobe. The secondary areas are located partly on the 

 lateral aspect of the occipital lobe and partly in the supra-marginal 

 and angular convolutions of the parietal lobe. 



Focal lesions of the primary area on one side are followed by lateral 

 homonymous hemianopsia, which, however, does not involve, as a rule, 

 the fovea or macula. 1 It is, therefore, the area of homonymous half-retinal 



1 In a consideration of this subject certain facts connected with visual perception, both in 

 physiologic and pathologic conditions, must be kept in mind. Thus, visual sensation may arise 

 from stimulation of either the central portion, the macula, or the peripheral portion of the retina 

 or both. In the first instance the vision is termed central or macular; in the second instance, 

 peripheral or retinal. Macular vision is clear, sharp, and distinct; retinal vision progressively 

 indistinct from the center toward the periphery. Division of one optic tract is followed, in con- 

 sequence of the partial decussation of the optic nerve-fibers at the chiasma, by a loss of function 

 in the outer two-thirds of the retina of the same side, both in the central (macular) as well as in 

 its peripheral portions, and the inner one-third of the retina of the opposite side. To this condition 

 the term hemianopsia has been applied. As a result of this want of functional activity of these reti- 



