1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 117 



other experiments, only the longitudinal extent of the supplied cortex, 

 since in the monkey the striate cortex does not reach the convex face 

 of the lips of the fissure except along both ascending and descending 

 branches. Of particular interest is the fact that the narrow oblong 

 strip of cortex supplied by the degenerated bundle at its oral begin- 

 ning where the striate area appears in the bottom of the fissura cal- 

 carina, represents also a narrow zone (dorsal half of the narrow striate 

 area) and increases in extent farther caudad toward the occipital 

 pole in the same way as the striate area extends toward the edge of 

 the upper lip. The shape of the supplied segment of the striate area, 

 accordingly, resembles that of a narrow triangle with its sharp point 

 at the anterior beginning of the calcarine striate cortex, its wider end 

 turned occipitalward. 



From the above description it is clear that a small segment of the 

 external geniculate body, in the present experiment the internal seg- 

 ment, gives origin to a number of central visual fibers which form 

 during almost their entire course a well delimited, compact bundle 

 with a definite course and position (except during its passage through 

 the internal capsule Avhere its fibers lie somewhat scattered), which 

 bundle supplies a small, well defined, triangular segment of the area 

 striata, here a "boundary zone" of the upper lip of the fissura cal- 

 carina. No other cortical region of the striata area (lower lip, external 

 face of the occipital opercle, occipital pole) or of the peri-parastriate 

 area (areas 18 and 19 of Brodmann) stands in connection with the 

 inner segment of the external geniculate body. The supplied cortical 

 triangle stretches along the entire upper lip of the calcarine fissure, 

 as far as the latter contains the striate cortex, and is slightly twisted 

 spirally around the axis of the fissure. The fiber supply of the tri- 

 angular cortical segment is everywhere about equally abundant and 

 uninterrupted, nowhere showing gaps. (Compare Experiment I.) 

 On numerous well stained sections dense bundles of degenerated fibers 

 approach the upper lip of the fissure to enter finally the striate cortex 

 (fig. 57, 65). 



These features regarding the origin, course, and termination of the 

 single fiber bundle degenerated in this experiment when taken with 

 facts established in the four remaining experiments corroborate the 

 view that the individual fibers of the visual radiation which take origin 

 in closely neighboring portions of the external geniculate body, form 

 compact bundles and enter closely neighboring portions of the visual 

 cortex (this meaning the "neighboring" or "spatial" arrangement of 

 fiber fascicles of the visual radiation). (See Chapter XIX.) 



