OAPSTJLA INTERNA, CORPUS STRIATUM, INTBRBRAIN-GANGLIA. 249 



in Pig. 124. You must understand that the two hemispheres are in part re- 

 moTcd, and bear in mind that their coronal fibers passed downward from 

 above into the knee-shaped, white line of the internal capsule. The portions 

 of the capsule formed by fibers coming from the frontal and occipital lobes 

 lie in part in the plane of the section. A few words now in explanation of 

 this section. 



The frontal, occipital, and temporal lobes are recognized immediately. 

 The temporal lobe lies over the island of Eeil, and thu.s partly conceals it. 

 As in Fig. 135, you see the corpus callosum in front cut transversely, and 

 adjoining it the septum pellucidum, at the posterior end of which the pillars 

 of the fornix ascend. 



Anteriorly, external to the septum, lies the head of the nucleus cau- 

 datus, which is cut into in this section. Its tail, which was seen passing 



Fig. 161. — Nucleus caudatus exposed along its entire length (diagram- 

 matic). Ammonsliorn, Comu Ammonis. Biechlappen, Olfactory lobe. Ventrikel, 

 Ventricle. 



along the side of the thalamus in Fig. 135, is not visible. It is contained in 

 the part of the brain removed. Only a small portion of it is still to be 

 seen, posteriorly and externally, near to the cornu Ammonis. The above 

 sketch, which represents a nucleus caudatus dissected out, shows how this 

 condition is brought about. 



The tail of the nucleus caudatus bends around the brain-stem in a 

 gentle curve, and is to be traced almost to the apex of the inferior horn of 

 the lateral ventricle. The entire nucleus must consequently be cut twice 

 in every horizontal Section made through the deeper planes of the brain. 

 This is shown by the line a 6 in Fig. 161. 



Thick tracts of fibers are seen external to the head of the nucleus cau- 

 datus. They come from the cortex of the frontal lobe, and contain the 



