190 ANATOMY OF THE CENTEAL NEETOUS SYSTEM. 



the brain is decidedly thicker than during the' festal period, but the corpus 

 striatum still projects from the floor into the cavity of the ventricle, as in 

 that section. The outer fissure is now obliterated, since the coronal fibers 

 from the cortex have increased in late embryonic life. At the bottom of the 

 great fissure the ventricle is seen to be covered by the dense transverse fibers 

 of the corpus callosu.m. To these there ascend from below the two pillars of 

 the fornix, leaving the ventriculus septi pellucidi free between the thin mem- 

 branes of the septum pellucidum. They project freely into a cavity: the lat- 

 eral ventricle. This cavity is bounded without by the corpus striatum, imst 

 here it may be beautifully seen how the corpus striatum is penetrated, and 

 apparently divided into two ganglia, by the thick masses of fibers forming 

 the internal capsule. In the lenticular nucleus — that is to say, in the outer 

 part of the corpus striatum — three divisions are easily distinguished. Only 

 the outer one of the three parts, the putamen (shaded heavily in Fig. 137), 

 is regarded in common with the nucleus caudatus as a source of fibers. The 

 significance of the two inner parts, globus pallidus, is not clear as yet. Some- 

 times the globus pallidus consists of three or more divisions. Externally to 

 the lenticular nucleus there lies a thin, gray mass in the wall of the hemi- 

 sphere known as the claustruni. The space between it and the lenticular 

 nucleus is called the capsula externa. Still farther out lies the cortex of the 

 island of Reil. The gray mass in the fioor of the middle ventricle belongs 

 to the wall of the infundibulum, the tuber cinereum. With its continuations, 

 it is spoken of as the central gray matter of the'ventricle. At the point where 

 this central gray matter and the cortex of the temporal lobe are continuous 

 with one another there lies a large, roundish nucleus: the nucleus amygdalae. 

 It probably stands in some relation to the terminal apparatus of the olfactory 

 nerve. Prom the neighborhood of the nucleus amygdalfe, probably from the 

 nucleus itself, there arises a portion of those bundles of fibers which pass as 

 the stria cornea between the thalamus and the nucleus caudatus. 



We know from comparative anatomical investigations that the space between 

 the infundibulum and the nucleus amygdalae, shown in horizontal section in the 

 illustration and included with the central gray matter, is a cortical region A-\-hieh is 

 very much atrophied in man. It is designated as the olfactory field. 



Between the pillars of the fornix the anterior commissure is seen (Fig. 

 185). Its fibers curve backward as they pass through the corpus striatum. 

 Thus it happens that we again meet with them in transverse section, just 

 below the outer part of the lenticular nucleus (Fig. 127, below and to the 

 left). 



I cannot urge you too strongly to look up in the fresh brain all the 

 structures just mentioned and to become acquainted with their relations by 

 making preparations of your own. Descriptions and illustrations will prob- 



