Chapter X 



ORIGIN, COURSE, TERMINATION, AND INTERNAL 

 ORGANIZATION OF THE AUDITORY RADIATION 



In two of the reported experiments (Experiment I and II) fibers 

 forming the auditory radiation, besides the thalamo-cortieal radiation 

 described in the foreg'oing: chapters, and the visual radiation to be 

 described later, were interrupted and degenerated. 



In Experiment I by the lesion described previously (see Chapter 

 V) the internal g-eniculate body (Cgm in corresponding figures) was 

 partly destroyed directly and partly separated from the hemisphere 

 (figs. 33-35). In Experiment II the internal geniculate body was 

 also directly destroj^ed, but in addition the auditory radiation was 

 completely interrupted close to its origin (figs. 51, 52, especially fig. 

 51). In both experiments the auditory radiation (ar in corresponding 

 figures) apparently degenerated completely, particularly in Experi- 

 ment II, thus rendering it possible to trace the entire course of the 

 radiation from its origin to its termination in the cortex of the Sylvian 

 fossa (figs. 2'6-31, 33, 34 and figs. 47-51, and perhaps x in figs. 52-54). 



Since in both experiments the finding's are nearly identical, the 

 description given here is the result of both experiments. 



The course of the auditory radiation (ar in accompanying figures), 

 is as follows : From the internal geniculate body a strong bundle of 

 closely assembled degenerated fibers turns in a lig'ht arc laterally, 

 entering the most ventral portion of the internal capsule immediately 

 above the lateral geniculate body (Cgl in figs. 30, 31, 33, 51). Near 

 their origin while still within the between-brain, but also in the 

 internal capsule, it is not easy to distinguish between the auditory and 

 the ventral somatic sensory fibers, the latter originating from the most 

 ventral portion of the thalamus and forming the ventral bundles of the 

 thalamo-cortieal radiation (figs. 30-32, 51; compare Chapter V). 

 The majority of the auditory fibers, however, form one single strong 

 bundle or rather a fiber lamina, having nearly a horizontal position. 

 Both somatic sensory and auditory fibers can be kept apart better 

 more laterally toward the putamen where they diverge from one 

 another. Ventral somatic sensory bundles soon after they enter the 



