38 LECTURES ON THE CENTRAL NERVOUS SYSTEM. 



striatum rises from the floor just as shown in that section. The 

 outer fissure has now disappeared, but it may be considered as 

 occupying the situation shown by the dotted line on the right 

 side. 



At the bottom of the great fissure you can see the ventricle 

 covered by the thick cross-fibres of the corpus callosum. To 

 these there pass from below the two pillars of the fornix, 

 leaving the ventriculus septi pellucidi free between the thin 

 layers of the septum pellucidum. They project freely into a 

 cavity, the lateral ventricle. This cavity is bounded exteriorly 

 by the corpus striatum. Just here you can see beautifully how 

 the corpus striatum is penetrated by and apparently divided 

 into two ganglia by the thick masses of fibres of the internal 

 capsule. In the lenticular nucleus, that is, in the outer portion 

 of the corpus striatum, you can easily distinguish three divisions. 

 Only one of these three parts the external, shown most deeply 

 shaded, called the putamen may be regarded as a source of 

 origin of fibres, together with the nucleus caudatus. The 

 function of the two internal divisions (globus pallidus) is still 

 uncertain. The globus pallidus sometimes consists of three or 

 more divisions. External to the lenticular nucleus there lies a 

 thin, gray mass in the wall of the hemisphere, the claustrum. 

 The space between it and the lenticular nucleus is called the 

 external capsule. Farther out still lies the cortex of the island 

 of Reil. The gray mass on the floor of the middle ventricle 

 belongs to the wall of the infundibulum, the tuber cinereum. 

 It and its continuation are called the central (ventricular) gray 

 substance. At the point where this and the cortex of the tem- 

 poral lobe become continuous there lies a large, roundish nucleus, 

 the nucleus amygdalae. It probably stands in some relation to 

 the origin of the olfactory nerve. In its finer structure it re- 

 sembles the claustrum (Mendinol). Between the pillars of the 

 fornix you see the anterior commissure. Its fibres curve back- 

 ward as they pass through the corpus striatum. For this reason 

 we again meet them on cross-sections of the brain, just below 



