38 University of California Publications in Anatomy [Vol. 2 



which occupies the lower wall of that fossa or the upper wall of the 

 superior temporal convolution (TJ. Afferent fibers which enter the 

 oral portion of that temporo-parietal receptive area (in the Sylvian 

 fossa) are mostly thin, while those reaching the caudal portion of that 

 area along the posterior limb of the Sylvian fissure, have, to a consid- 

 erable extent, quite a coarse caliber. This new posterior Sylvian recep- 

 tive field stretches along the entire posterior (occipital) extremity of 

 the Sylvian fissure and is here separated from the proper somato- 

 sensory region by a narrow strip of cortex covering the convexity of 

 the inferior parietal (angular) convolution {PI in figs. 52, 53). The 

 latter receives, in this experiment, few if any afferent fibers. How- 

 ever, attention must be called to the fact that this posterior Sylvian 

 region is in reality practically entirely concealed in the Sylvian fissure ; 

 the shaded area along that fissure {x in figs. 2, 10, 24) indicates only 

 the position of that region inside of the fissure as well as its longi- 

 tudinal extent. In view of the fact that beside a portion of the thala- 

 mus and of the internal capsule, also a portion of the globus pallidus 

 and of the putamen was injured in the present experiment, it is impos- 

 sible to decide whether the last described afferent fibers do actually 

 and exclusively originate from the ventral thalamus, or whether, per- 

 haps, they may arise elsewhere. It would hardly seem that they belong 

 to the intrahemispheric association systems and, at least the stronger 

 ones among them, are likely to be actual afferent fibers arising from 

 the ventro-lateral nucleus of the thalamus and perhaps also from the 

 metathalamus (internal geniculate body?). In that case the described 

 posterior Sylvian region {x) would represent a portion of the common 

 auditory projection cortex {a in figs. 2, 10), or a special receptive area 

 of an as yet unknown functional significance (see Chapter XI, 2). 



Experiment III 



In this experiment only a portion of the entire thalamo-cortical 

 radiation was interrupted within the posterior limb of the internal 

 capsule (fig. 66). The split-like lesion {L in the figure) is located 

 between the dorsal comer of the thalamus and the Sylvian sulcus, the 

 level of the injury approximately corresponding with the planes of 

 figures 33, 34 and 52 of both foregoing experiments. Interrupted by 

 the injury, a dense bundle of ascending thalamo-cortical fibers {sr) 

 degenerated completely, while other bundles of the thalamo-cortical 

 radiation remained normal. The lundle which was thus caused to 



