298 THE NERVOUS SYSTEM 



efferent fibers are contained in the optic radiation. They arise in the cortex 

 about the calcarine fissure and terminate in the pulvinar, lateral geniculate 

 body, and superior colliculus of the corpora quadrigemina (Fig. 162). A corti- 

 corubral tract descends from the frontal lobe through the posterior limb of the 

 internal capsule to end in the red nucleus of the mesencephalon. There do not 

 appear to be any strictly corticostriate fibers, but, according to Cajal (1911), 

 collaterals from the corticospinal fibers are given off to the corpus striatum. 

 The efferent projection tracts which we have considered all have their origin in 

 the neopallium. 



There are several projection tracts from the rhinencephalon, and of these the 

 most important is the fornix. The fibers of this fascicle take origin in the hip- 



Cingulu 



Inferior longitudinal 

 fasciculus 



Fig. 226. Some of the important association bundles projected upon the medial aspect of the 

 cerebral hemisphere. (Sobotta-McMurrich.) 



pocampus, follow an arched course already described, and, entering the dien- 

 cephalon, terminate in part in the mammillary body and in part in the teg- 

 mentum of the brain stem (Fig. 205). 



The frontal olfactory projection tract arises from the gray matter of the ol- 

 factory peduncle and the lateral olfactory gyrus. It enters the brain stem and 

 terminates in the pons and the medulla oblongata (Fig. 211). 



Association Fibers. The various parts of the cortex within each hemisphere 

 are bound together by associatiorrfibers of varying length. The short associa- 

 tion fibers are of two kinds: (1) those which run in the deeper part of the cortex 

 and are designated as intracortical, and (2) those just beneath the cortex, which 

 are known as the subcortical fibers. The greater number of these subcortical 

 association fibers unite adjacent gyri, curving in U-shaped loops beneath the 



