

THE FORE-BRAIi 



the medial lemniscus; (2) the fibers of optic radiation, from the lower visual centers 

 to the cortex of the occipital lobe; (3) acoustic fibers, from the lateral lemniscus to 

 the temporal lobe; and (4) fibers which pass from the occipital and temporal lobes 

 to the nuclei pontis. 



The fibers of the internal capsule radiate widely as they pass to and from the 

 various parts of the cerebral cortex, forming the corona radiata (Fig. 745) and 

 intermingling with the fibers of the corpus callosum. 



The external capsule (capsula externa) (Fig. 742) is a lamina of white substance, 

 situated lateral to the lentiform nucleus, between it and the claustrum, and con- 

 tinuous with the internal capsule below and behind the lentiform nucleus. It 

 probably contains fibers derived from the thalamus, the anterior commissure, and 



e subthalamic region. 



R. oculomotor nerve 



L. oculomotor nerve 



Superior peduncle / 

 Pyramid 



Inferior peduncle 



FIG. 745. Dissection showing the course of the cerebrospinal fibers. (E. B. Jamieson.) 



(I 



The substantia innominata of Meynert is a stratum consisting partly of gray and 

 iartly of white substance, which lies below the anterior part of the thalamus 

 and lentiform nucleus. It consists of three layers, superior, middle, and inferior. 

 The superior layer is named the ansa lentiformis, and its fibers, derived from the 

 medullary lamina of the lentiform nucleus, pass medially to end in the thalamus 

 and subthalamic region, while others are said to end in the tegmentum and red 

 nucleus. The middle layer consists of nerve cells and nerve fibers; fibers enter it 

 from the parietal lobe through the external capsule, while others are said to con- 

 nect it with the medial longitudinal fasciculus. The inferior layer forms the main 

 part of the inferior stalk of the thalamus, and connects this body with the temporal 

 lobe and the insula. 



The stria terminalis (icenia semicircularis) is a narrow band of white substance 

 situated in the depression between the caudate nucleus and the thalamus. Ante- 

 riorly, its fibers are partly continued into the column of the fornix; some, however, 

 >ass over the anterior commissure to the gray substance between the caudate 



