1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 213 



of Flechsigf, supported by Henschen and a number of other neu- 

 rolog'ists, though their conceptions must be modified somewhat. There 

 is another related question which must, however, be settled by physio- 

 logical experiments and by clinical studies. Are the projection areas 

 to be regarded exclusively as "gateways" of the cerebral cortex for 

 the incoming impulses, comparable to the switchboard of a telephone 

 station, as claimed by Flechsig and Henschen, or, do they participate 

 likewise in higher integrative processes, as assumed by other neu- 

 rologists (Niessl von Mayendorf), thus depriving the intercalated 

 regions of the exclusive monopoly of these higher processes? This 

 problem exceeds the scope of the present treatise and will be dealt 

 with in the future after the various association and other connections 

 of the established cytoarchitectural regions have been analyzed.^ On 

 the other hand, at least some of the intercalated association regions 

 of the hemisphere do not appear to be concerned exclusively with 

 higher processes, since they have subcortical connections of their own, 

 although, so far as ascertained, these are efferent tracts. Thus the 

 area peri-parastriata, for example, stimulation of which results in 

 various eye movements (Baranyi-Vogt, Foerster, 1929-), is the place 

 of origin of the occipital cortico-mesencephalic tract (Experiment 

 XV), while the existence of a similar efferent tract is doubtful in the 

 case of the striate area proper (Experiment XIV, figs. 87-94) though, 

 according to Flechsig's formula such efferent tracts should descend 

 from each receptor area of the hemisphere, and actually do exist both 

 in the precentral and in the postcentral cortex as demonstrated by 

 other experiments of mine involving small injuries strictly limited in 

 some cases to the precentral, in others to the postcentral region 

 (Experiments VI, VII, VIII, figs. 77, 78, 79, 80, 81). As shown in the 

 preceding pages, not only is the principle of localization thoroughly 

 valid with respect to the "gross" relationship to the cerebral cortex 

 of the three afferent paths investigated and to their several functions, 

 but, as demonstrated above, the same principle obtains in the internal 

 organization of all three afferent paths, being most clearly expressed 



1 Compare the remarkable experiments of Foerster (1929) and Foerst«r-Penfield 

 ■who electrically stimulated the area striata and the area peri-parastriata in con- 

 scious human subjects. (Compare footnote, p. 217.) 



2 In Foerster 's recent experiments in man no eye-movements resulted if the 

 striate area (field 17) was stimulated alone, which had been obtained when the 

 stimulus was applied to the peri-parastriate area (fields 18-19). Biemond found 

 in experiments with monkeys fibers descending from the striate area to the external 

 geniculate body and to the superior colliculus. It is, however, apparent that 

 these fibers arise from areas 18 and 19, since in all experiments of Biemond these 

 areas were partially damaged. 



