34 University of California Puhlications in Anatomy [Vol. 2 



latter. In fact, the lesion misses the rostral portion of the anterior 

 limb of the internal capsule, destroying' only its middle and caudal 

 segments. Moreover, the capsular lesion enters the ventral thalamic 

 and subthalamic regions (figs. 50-52). Within the diencephalon, a 

 greater part of the zona incerta and of the thalamic or subthalamic 

 region in front of it, escaped the injury. Thus both fields of Forel, 

 the stratum intermedium of the peduncle and the corpus subthala- 

 micum of Luys remained almost entirely outside the injury. Part of 

 the injury follows the ventral portion of the external medullary lamina 

 passing through the ventro-lateral nucleus of the thalamus as far 

 medialward as the lateral boundary of the arcuate nucleus of Forel 

 and approaches the nucleus of Luys. Other thalamic nuclei were not 

 directly injured. Since the capsular lesion, however, occupies the 

 entire posterior limb of the capsule, hence separating a preponderance 

 of the thalamus from the hemisphere, it must be assumed that a 

 greater jiart of the thalamo-cortical radiation was interrupted regard- 

 less of the amount of the thalamic injury. The thalamo-cortical con- 

 stituents which possibly escaped injury are those fibers originating in 

 the most caudal portion of the lateral nucleus, including the pulvinar 

 (figs. 52, 53), and above all, those arising from the extreme rostral 

 segment of the lateral nucleus (fig. 47). 



The number of thalamo-cortical fibers interrupted in this experi- 

 ment exceeds considerably that of Experiment I due to the extent of 

 the lesion and to its location where all thalamo-cortical fibers con- 

 verge to form a compact fiber system (for explanation see Experi- 

 ment I). For this reason, the present experiment offers less oppor- 

 tunity for studying the origin, course, and termination of constituent 

 divisions of the radiation. On the other hand, the completeness of its 

 degeneration demonstrates excellently that entire fiber system. 



The first feature to be discerned is the trend of by far the larger 

 number of all thalamo-cortical fibers toward the dorsal and dorso- 

 lateral regions of the cerebral cortex, corresponding to the convexity 

 of the hemisphere, the remainder turning medially, toward the inter- 

 hemispheric cortex and laterally, toward the opercula. The fibers 

 leading dorsalward are of a somewhat larger caliber. The coarsest 

 are those tending toward the convexity of the dorsal segment of both 

 central convolutions and toward the cortex coating the upper extremity 

 of the sulcus centralis, while those intended for the interhemispheric 

 cortex around the cingular sulcus, as well as those for the precentral 

 and postcentral opercula, are perceptibly thinner. Fine fibers are 



