1932] Poliak: Afferent Fiber Systems, PHmate Cerebral Cortex 53 



area for detailed (special) movements, area praecentralis gig^anto- 

 pyramidalis or field 4 of Brodmann, and also field 6 of that inves- 

 tigator. (Compare Economo-Koskinas, pp. 288, 312, 538.) 



I would here touch upon a few points in the work of previous 

 investigators which are not in accord with the present results. Sachs 

 (1909) in his experimental work on the thalamus observ^ed almost all 

 thalamo-cortical fibers to turn toward the precentral and frontal 

 cortical regions, the reverse of my Experiment III. The lesions in his 

 experiments, besides being too small to permit an estimate of the 

 numerical distribution of thalamo-cortical fibers to various portions 

 of the somato-sensory cortex, were practically all situated within the 

 anterior or rostral half of the thalamus, leaving the pulvinar and the 

 posterior half of the thalamus mostly unaltered. From what has 

 already been said about the internal arrangement or the segmentation 

 of the thalamo-cortical radiation it seems clear, that in Sach's experi- 

 ments, preponderantly, if not exclusively, the anterior or the rostral 

 portion of the thalamic radiation was partly caused to degenerate. 

 In the work of other investigators (Probst, Roussy), where extensive 

 lesions of the thalamus and internal capsule were produced, there was 

 also a degeneration of both visual and auditory^ central paths. These 

 latter fibers were not sufficiently discriminated from the proper 

 thalamo-cortical radiation. By confounding both geniculo-cortical 

 radiations with a portion of the thalamo-cortical radiation proper, 

 these investigators erroneously claimed a greater part of the cortical 

 surface, including the parieto-occipital lobe and a part of the temporal 

 lobe, as the somatic sensory region. JMonakow fell into similar error, 

 although in his case this was more excusable, for his technique was 

 inadequate. He proclaimed the occipito-tectal efferent fiber system 

 which passes through the ventral pulvinar as a pulvinaro-cortical and 

 mesencephalo-cortical afferent path, (Compare fig. 96.) 



Besides the areas on both sides of the sulcus centralis and the 

 neighboring portion of the cortex on the internal face of the hemi- 

 sphere (rendering that sulcus comparable to the fissura calcarina), 

 all of which might justly be regarded as the somatic sensory region in 

 a broad sense (Brodmann 's areas 1, 2, 3, 4, 5, 6, 7, and 43), there has 

 been found in Experiment II, a special temporo-parietal (posterior 

 Sylvian) receptive region also receiving afferent fibers (area x in 

 figs. 2, 10, 24) . Because of the location of the lesion in that experiment, 

 as explained in the foregoing paragraphs, it cannot be denied that 

 some of the fibers entering that cortical region might be associational 



