THE COMMISSURES. 



243 



medulla oblongata, into the spinal cord, where the fibers enter the gray 

 substance at various levels. 



Taken together, these fibers passing downward from the cortex are 

 designated as the corona radiata. You will not form a wrong idea of this 

 if the thalamus is imagined as placed free under the overarching dome of 

 the cerebral cortex, and it is then assumed that nerve-fibers pass to it from 

 all parts of the cortex. Tracts of fibers enter it from the cortex of the 

 frontal, parietal, temporal, and occipital lobes — perhaps tracts of fibers from 

 the cortex at the entrance to the fossa Sylvii and from the cornu Ammonis 



Ccl4 



Ooa 



Fig. 158. — Posterior portion of the right hemisphere seen from the inner 

 surface. By teasing out with forceps, the radiation of fibers from the posterior 

 end of the corpus callosum {SplcHiim, Ccl*) is shown. The mass under the 

 corpus callosum is the fhalamus opticus (Tho). On the wall of the ventricle 

 surrounding it, the tapetum (Tap). A part of the fasciculus longitudinalis in- 

 ferior (Fli) is also to he seen in the illustration. The thalamus has under it the 

 pes pedunculi (B). The other letters refer to structures that will be mentioned 

 in the text later on: Rdf, Vicq d'Azyr's bundle; Saf, Fornix; Cca, Corpus 

 eandicans; II', Nervus opticus; Fcp, Forceps. 



