THE CEREBRUM 169 



64, p. 141), cortico-bulbar tract, and cortico-pontile tracts (pp. 

 187 and 289). 



The gray matter of the corpus striatum is gathered into two 

 principal masses, the caudate nucleus and the lentiform nucleus 

 (so-named from their shapes), and most of the projection fibers 

 pass between these nuclei in a wide band of white matter known 

 as the internal capsule. The broken ends of the internal capsule 

 fibers are seen in the dissection shown in Fig. 45 (p. 114). As 

 these fibers radiate from the internal capsule toward the cortex 

 they are called the corona radiata (Fig. 79). The external 

 capsule is a thinner sheet of fibers externally of the lentiform 

 nucleus (Figs. 79 and 80). Figure 79 illustrates a transverse 

 section through the cerebral hemisphere, showing the relations 

 of the thalamus and corpus striatum. 



The exact arrangement of the functional systems of sensory 

 and motor projection fibers within the internal capsule is a 

 matter of great clinical importance; for a considerable propor- 

 tion of apoplexies and other cerebral diseases result from hemor- 

 rhage or other injury of the internal capsule causing destruction 

 of some of its fibers. A partial paralysis will result, whose symp- 

 toms will depend upon the particular functional systems of pro- 

 jection fibers affected. Figure 80 illustrates the arrangement 

 of some of the systems of fibers of the internal capsule as seen 

 in a horizontal section through the cerebral hemispheres. 



The olfactory centers of the cerebral hemispheres and the 

 cerebral cortex will be considered in chapters which follow. 



Summary. The cerebrum contains the primary centers for 

 the I, II, III, and IV pairs of cranial nerves, but most of its 

 substance is concerned with the higher centers for the correla- 

 tion of sensory impressions, especially those involved in the 

 psychic activities. The midbrain contains in the corpora quad- 

 rigemina important reflex correlation centers of sight and hear- 

 ing, and in the cerebral peduncle centers for the coordination of 

 movements. The diencephalon is devoted chiefly to various 

 types of correlation. It is divided into three parts, the thalamus, 

 the epithalamus, and the hypothalamus, the two last being 

 dominated by the olfactory system. The thalamus contains a 

 medial group of nuclei concerned with thalamic reflexes and the 

 affective experience and a lateral group of nuclei which discharge 



