1932] Poliak: Afferent Fiber Systems, Primate Cerehral Cortex 29 



part of the dorso-lateral nucleus, a part of the ventro-lateral nucleus, 

 and also a part of the central nucleus (Luys) of the thalamus (fi^s. 28- 

 31, 33), leaving- the remaining regions of the thalamus intact (fig. 27). 

 A part of the external geniculate body, the medial or the internal seg- 

 ment of its posterior "spur," and the internal geniculate body were 

 also directly destroyed (figs. 33-35). The longitudinal extent of the 

 injury occupies more than the caudal half of the thalamus ; the injury 

 decreases, however, rapidly in size oralward, leaving the oral segment 

 of the thalamus uninjured (fig. 27). Although its distance usually 

 ranges only 1-2 millimeters from the lateral border of the thalamus 

 and from the internal capsule, the lesion remains everywhere strictly 

 within the thalamus (figs. 28-31, 33, 34), except near the caudal 

 extremity of the pulvinar where the instrument reached the dience- 

 phalon (figs. 35, 36). Except in the most oral sections where the 

 lesion barely reaches these fiber layers (fig. 28), even the external 

 medullary lamina and the reticulate stratum of the thalamus remained 

 untouched by the lesion. 



In consequence of the injury a large number of fibers forming 

 the thalamo-cortical radiation {sr in corresponding figures) degen- 

 erated. To some extent they can be followed as separate bundles to 

 their respective cortical terminations. From the pulvinar proper, 

 especially from its dorsal portion, only fine, poorly myelinated fibers 

 arise. Of these, some have been traced to the near-by tail of the 

 caudate nucleus (fig. 35, upper lesion L), others through the internal 

 capsule to the putamen and globus pallidus. Scarcely any of these 

 fine fibers reach the cerebral cortex. However, the cortex might be 

 reached by a few fibers of medium size from the ventral portion of 

 the pulvinar. 



Fibers originating from the lateral nucleus of the thalamus, mostly 

 of fairly coarse appearance, emerge from every part of it into the 

 internal capsule as a broad stream. Immediately, or within a short 

 space, they turn dorsalward along the dorsal corner of the thalamus 

 toward the upper half of the hemisphere. Their further course and 

 ultimate cortical termination differs depending upon their thalamic 

 origin. Thus, bundles originating in the dorso-lateral nucleus and 

 consisting of thin, medium sized, and numerous coarse fibers proceed 

 for the most part directly upward to reach the uppermost sectors of 

 both central convolutions and the neighboring portion of the inter- 

 hemispheric cortex (figs. 29-31, 33). Other fibers, arising from the 

 ventral nuclear group of Monakow, also mostly of large caliber, pene- 



