1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 109 



Of particular interest was the study of the course and termination 

 of both compact deg^enerated bundles. At their be^nning- near the 

 lesion and immediately caudad to it, both bundles are composed exclu- 

 sively of degenerated fibers (figs. 37, 38) and contain fibers of a 

 different caliber : fairly coarse and finer fibers. While all the coarser 

 fibers were traced toward the visual cortex, a number of finer fibers 

 soon disappeared farther caudad thus revealing their different origin, 

 course, and significance. 



The two compact degenerated bundles have approximately a rhom- 

 boid and later a trapezoid shape, and occupy exclusively the external 

 sagittal stratum of the parieto-occipital lobes. This was especially 

 evident after a number of finer degenerated non- visual fibers had dis- 

 appeared. Yet even farther caudal, the number of fine fibers exceeds 

 that of the coarse, the latter representing only a minority of all fibers 

 composing the external sagittal stratum. 



On the whole, the afferent visual fibers, irrespective of their caliber, 

 preserve during their course occipitalward their position within the 

 external sa^ttal layer leaving the narrow internal sagittal layer and, 

 of course, the tapetum entirely free. 



Both compact degenerated bundles {in\ and vr.) preserve their 

 relative position to each other as far caudad as the occipital lobe and 

 can be distinguished as separate individual bundles (figs. 38^1). 

 Later on when they approach the striate cortex marked by the dotted 

 intracortical stripe in corresponding figures of sections through the 

 oecipital lobe, showing the striate area in its full extent, both bundles 

 gi-adually merge (fig. 42). This apparent mixing of fibers formerly 

 belonging to separate bundles, apparent only on a superficial exami- 

 nation, is the consequence of the considerably changed topographic 

 conditions in the white matter of the occipital lobe. The fibers, 

 namely, when they reach the occipital lobe, change from a longitudinal- 

 sagittal direction into an ascending course or turn gradually laterally 

 or medially to reach their special segments of the striate area. As a 

 matter of fact, even in the occipital lobe near their termination the 

 two separate degenerated zones are fairly well discernible, and their 

 fibers can be traced individually to different portions of the striate area. 



It was of interest to notice that no degenerated fibers of the sagittal 

 strata, be they coarse or fine, either from the two separate bundles or 

 from scattered degenerated fibers turn toward the cortex of the 

 parieto-occipit-al lobe except when they approach the striate area. 

 Before they enter the striate cortex they form laterally to the external 



