1932] Poliak: Afferent Fiber Systems, Priimte Cerebral Cortex 127 



branches remaining free (lower fignre in fig. 4). Degenerated fibers 

 entering into the macular cortex are everywhere abundant, especially 

 around the sulcus carcarinus externus of Cunningham-Elliot Smith. 

 These fibers are mostly delicate. 



Both the superior and inferior horizontal branches of the visual 

 radiation contain none or only a few scattered degenerated fibers, 

 especially none corresponding with the main undivided portion of the 

 calcarine fissure. Consequently in this experiment, the scattered or 

 solitary degenerated fibers, without mentioning the absence of the 

 compact bundles of these found in the preceding four experiments, 

 reach neither the upper nor the lower lip of the calcarine fiissure. 



The peri-parastriate area of Elliot Smith, the field 18-19 of Brod- 

 man, remains completely free from any degenerated fibers, these 

 strictly respecting the boundaries of the striate cortex, as in the pre- 

 ceding experiments. 



A few of the degenerated fiber bundles enter the opposite hemi- 

 sphere through the corpus callosum. They consist of thin fibers inter- 

 rupted in the tapetum by the same lesion that interrupts the macular 

 fibers of the external sagittal layer. These fibers evidently belong to 

 the callosal system. 



As the present experiment well demonstrates, the intermediate or 

 the perpendicular branch of the ^asual radiation neither mingles with 

 the upper nor with the lower horizontal branch of the radiation. Its 

 course is directly toward the occipital pole in contradistinction to both 

 horizontal branches which reach their respective lips of the calcarine 

 fissure by devious ways: the upp^r one bends gradually in a spiral- 

 like fashion around and above the upper edge of the lateral ventricle, 

 and the lower one goes below the lower edge of the same ventricle. 

 (Compare Chapter XVI.) The macular branch of the visual radiation 

 faces during almost its entire oral-caudal course the posterior horn of 

 the lateral ventricle on its lateral side. This branch enters solely the 

 portion of the striate area covering the occipital operculum and the 



Fig. 13, Experiment V-A. This figure demonstrates the position of the macular 

 portion of the visual radiation, the so-called "macular bundle" (M), within the 

 sagittal fiber layers (w) of the occipital lobe, degenerated after a localized injury 

 to these layers (L), and the course and entry of the macular fibers into the 

 macular portion of the striate area covering the lateral face of the occipital 

 operculum (Oo) and the tip of the occipital lobe. The macular portion of the 

 visual radiation (M) forms its intermediate or perpendicular branch; the superior 

 (vrs) and the inferior horizontal branch (vri) of the visual radiation which, in the 

 monkey, enter into the upper and lower lip of the calcarine fissure (Fo) respec- 

 tively, retain in this experiment normal fibers. (Compare with fig. 4; for 

 explanation see Chapter XVI and XVII.) 



