182 University of California Puhlications in Anatomy [Vol.2 



yet macular vision will be unaffected if the posterior portion of the 

 striate area and the macular portion of the visual radiation remain 

 normal. (Such a combination of destruction can also occure bilaterally, 

 in both hemispheres, leaving macular cortex and macular radiation 

 intact) . Here, however, there is likely to be some impairment of \'ision, 

 especially of the higher cognitive processes, even if the macular cortex 

 is not directly affected, since its association and other connections will 

 be interrupted. If the pathological process penetrates deep enough 

 either from the internal or external face of the hemisphere and attains 

 the vertical branch, or if it extends over the posterior portion of the 

 striate area (occipital pole), the initial incomplete hemianopsia will 

 become complete, the macular vision preserved at the beginning will 

 finally be destroyed. In such a case the vertical dividing line between 

 the blind and normal halves of the visual fields will pass exactly 

 through the points of fixation.^ ° 



It is clear from the foregoing that the hypothesis of a bilateral 

 cortical representation of the macula besides being hardly consistent 

 with a point to point macular projection proved by the existence of 

 small, sharp macular scotomata, is neither anatomically justified, 

 nor necessary to explain the preser\'ation of macular vision obser\^ed 

 in many cases of hemianopsia. The projection of the maculae upon 

 the cerebral cortex must be imagined as similar to that of the extra- 

 macular binocular portions of the retinae. The macula is di\dded by 

 a vertical meridian into two halves, each of these being projected upon 

 another hemisphere. This is accomplished in such a way as to bring 

 homonymous halves of both maculae in connection with one hem- 

 isphere only. Accordingly, when the visual cortex of one hemisphere, 

 or only the macular cortex or its afferent fibers are completely 

 destroyed, the result will be a complete and lasting homonymous 

 macular hemianopsia with the vertical line passing exactly through 

 the points of fixation and dividing hemianoptic halves of both macular 

 visual fields from the opposite halves remaining in function. Nor do 

 the theoretical arguments brought forward in support of the hypoth- 

 esis of a double cortical representation of the total macula seem to be 



10 The peculiar arrangement of the various segments of the visual radiation, 

 as found in the present study, explains also the often observed complete hemia- 

 nopsia in cases where the lesion lies close to the geniculate body. Here all 

 the fibers, both macular and "peripheral," lie closely assembled and are 

 likely to be interrupted by a single lesion, while more posteriorly the macular 

 fibers take a protected position on the outer side of the lateral ventricle. This 

 is an additional argument which renders the supposition of the decussating 

 macular fibers superflous. 



