72 University of California Piihlications in Armtomy [^'ol. 2 



internal capsule (% 44 of Experiment II, fig. 78 of Experiment VII, 

 figs. 80, 81, 83 of Experiment VIII, fig. 85 of Experiment IX) ; 



(2) also numerous yet somewhat stronger fibers to the globus 

 pallidus entering it by its dorsal extremity (tractus cortico-pallidalis, 

 figs. 78, 79 of Experiment VII, figs. 81, 82 of Experiment VIII) ; 



(3) fairly thin fibers to the red nucleus (tractus cortico-rubralis, 

 fig. 85 of Experiment IX), and 



(4) also fairly strong and medium sized fibers in considerable 

 numbers to the stratum intermedium of the peduncle and to the sub- 

 stantia nigra of Soemmering (tractus cortico-peduncularis and cortico- 

 nigralis), as far caudalward as the substantia nigra extends, descend- 

 ing partly by way of the median fillet (figs. 83, 84 of Experiment 

 VIII). (Thus the substantia nigra and the neighboring grey matter 

 appear as an important subcortical motor mechanism being under a 

 direct influence of the frontal-precentral cortex; this explains the 

 absence of changes in the nigral cells in experiments where the frontal 

 cortex alone M'as removed) ; 



(5) besides the well-known cortico-spinal, cortico-bulbar, and 

 numerous associational and callosal fibers. 



3. SOMATOSENSORY RADIATION 



Primary interest in this investigation was focused on the origin, 

 course, and termination of the thalamo-cortical radiation. It was 

 found that these fibers (sr in corresponding figures), originate from 

 the entire lateral nucleus of the thalamus, that is, from both the 

 ventro-lateral and the dorso-lateral nucleus as far dorsally as the 

 neighborhood of the caudate nucleus, and not just from the narrow 

 lateral zone of the ventro-lateral nucleus. In a word, it is at least the 

 lateral nucleus of the thalamus in its entire dorso-ventral and medio- 

 lateral extent situated between both medullary laminae which is the 

 terminal station for the lower ascending somatic sensory tracts as well 

 as the point of departure of the uppermost link of the afferent somatic 

 sensory system, the thalamo-cortical radiation. (Compare Flechsig, 

 1920, p. 28.) This thalamic radiation is a huge fiber system which 

 uses not only the posterior limb but to a certain extent as well, the 

 anterior limb of the internal capsule on its way to the cortex. In the 

 internal capsule at the level of the caudate nucleus all more caudal 

 thalamo-cortical fibers converge and come to lie close together since 

 here they all must pass the relatively narrow space between the caudate 



