82 University of California Puhlications in Anatomij i'^'oi.. 2 



internal capsule turn dorsally in their ascending course alon^ the 

 inner border of the putanien and partly also through the latter 

 nucleus, as described before. Auditory fibers remaining' horizontal or 

 bending slightly ventralward reach the external capsule by penetrat- 

 ing through the ventral edge of the posterior portion of the putamen. 

 Besides, the single strong bundle of the auditory radiation while still 

 within the internal capsule, has on frontal sections through the hemi- 

 sphere a characteristic appearance (figs. 30, 31, 33, 51). It is com- 

 posed of short oblique fiber segments arranged in a fairly regular way 

 side by side, thus making in reality a thick, dense fiber lamina, which 

 forms above the oral portion of the lateral geniculate body a cap or a 

 capsule. Practically all auditory fibers cross the ventral region of the 

 internal capsule in front of the plane where the central visual path 

 appears as the triangular field of Wernicke and gradually changes its 

 shape into the sagittal layers of the temporo-parietal lobes. Hardly 

 any of the auditory fibers pass through the visual radiation itself. 

 Thus both the visual and the auditory geniculo-cortical radiations, 

 although lying close together, are separated ; the auditory radiation 

 being more frontal, crosses at a right angle above the visual radiation, 

 while the latter takes a sagittal direction occipitalward. Arriving at 

 the internal contour of the putamen, the majority of auditory fibers 

 penetrate through the substance of that nucleus as strong or thin fiber 

 bundles in order to reach the external capsule, thus dividing the 

 ventral portion of the posterior putamen into several islets in exactly 

 the same way as has been described for the ventral thalamo-cortical 

 fiber bundles in relation to the dorsal ridge of the posterior putamen 

 (figs. 29-32, 50, 51). Many bundles of the auditory radiation turn 

 around the posterior edge of the putamen (figs. 33, 34). Within 

 the external capsule (figs. 32-34) auditory fibers are to some extent 

 mingled with other fibers arriving from the ventral thalamic region, 

 the latter ascending here doi-salward (on the real functional sig- 

 nificance of these latter fibers, x in figs. 52-54, nothing definite can 

 be said at present; see Chapters V, VI, and Chapter XI, 2). Here 

 pass also other fibers belonging to the anterior commissure and to 

 various association systems. Reaching the white substance of the 

 superior temporal convolution (TJ, auditory fibers proceed laterally 

 along' the cortex of the dorsal lip of this convolution; that is, some 

 close beneath the floor of the Sylvian fossa {FS), some through the 

 ventral spur of the claustrum. Generally, all fibers of the auditory 

 radiation, with a few exceptions, are strictly confined to the upper or 



