1932] Poliak: Afferent Fiber Systems, Primate Cerebral Cortex 7 



only does the postcentral convolution receive thalamic fibers, but the 

 precentral convolution as well ; though unfortunately in some of these 

 studies an indiscriminate inclusion of other aiferent systems into the 

 somatic sensory^ system led to almost the entire cerebral cortex being 

 accredited with thalamic representation. In numerous publications 

 Flechsig (1894, 1895, 1908, 1920, 1927) also attempted to establish the 

 termination of the thalamo-cortical radiation both in the precentral 

 and in the postcentral convolutions without, however, influencing 

 appreciably the current trend toward the dualistic conception. 

 Flechsig's findings lost power by his own indecision, for in one place 

 he speaks of both central convolutions as the terminal region of the 

 thalamo-cortical radiation, while in another he seems to refer primarily 

 or perhaps exclusively to the postcentral region. Nor was tliis state 

 of aifairs changed by Ramon y Cajal's discovery of the termination in 

 the precentral cortex of exogenous fibers which he declared to be of 

 thalamic origin, for Ramon y Cajal made the mistake of denying alto- 

 gether the existence of such fibers in the postcentral cortex (1909-11, 

 vol. 2, p. 639) ; E. Sachs arrived at a similar conclusion in his experi- 

 ments. The work of some modern investigators, for example, Meier- 

 Miiller (1919), Tsunesuke Fukuda (1919) and Minkowski (1923-24), 

 as well as earlier studies of Monakow (1895, 1914, p. 257), Anton- 

 Zingerle, Quensel (1906, 1910), Mingazzini (1913, 1914) and Rutis- 

 hauser, made at least probable a direct connection by aiferent fibers 

 between the anterior portion of the thalamus and the cortex of the 

 frontal lobe ; but this work was also ignored, perhaps because other 

 investigators (R. A. Pfeifer, 1920) described the thalamo-cortical 

 radiation as reaching the postcentral region only. There seems to have 

 been a feeling that results which opposed a strictly dualistic viewpoint 

 were due to errors (Horsley, 1909, was thus reproached by Bolton, 

 1911). In the remarkable physiological investigations on monkeys of 

 Minkowski (1917, 1923-24) and of Dusser de Barenne (1924, 1925) a 

 wider cortical region than the postcentral was found to be concerned 

 with sensation, namely, the postcentral, the parietal, and the frontal 

 (precentral) region as far as the arcuate sulcus. But the arguments 

 brought forward by Dusser de Barenne were regarded as insufficient, 

 and although some concessions were made (according to Foerster, 

 1925, 1927, the precentral region is an "accessory sensory field" with 

 respect to the "main" postcentral field ; see also Ariens Kappers, 1921, 

 2, p. 1201), the concept of the participation of the precentral cortex 

 in the sensory function was denied (Holmes, 1927). This appeared 



