978 CORPUS STRIATUM. [BOOK m. 



the hind limb of the capsule, Fig. 116, that while the nucleus 

 lenticularis is here at its greatest size, the head of the nucleus 

 caudatus (N~c), lying dorsal to the nucleus lenticularis and sepa- 

 rated from it by a considerable thickness of internal capsule, has 

 much diminished ; the same section moreover shews, ventral to 

 the nucleus lenticularis and clinging to the descending horn of 

 the lateral ventricle (l.v.d.), the extreme tip of the tail of the 

 nucleus caudatus (Nc) soon about to fuse with the small mass of 

 grey matter called the nucleus amygdalae (Na). A sagittal 

 (longitudinal dorso-ventral) section taken at some distance from 

 the median line (Fig. 119), shews the curved course of the larger 

 portion of the nucleus caudatus, the extreme head as well as the 

 latter part of the tail lying out of the plane of the section ; and a 

 similar section taken nearer the middle line (Fig. 122) shews how 

 the nucleus in the middle portion is broken up by bands of 

 fibres of the internal capsule traversing it, and thus contributing 

 to the striated appearance ; the same section also shews that the 

 globus pallidus as well as the putamen becomes continuous with 

 the nucleus caudatus. 



Thus when we speak of the corpus striatum as a whole we 

 mean a large mass of grey matter lying lateral to the optic thala- 

 mus, reaching nearly as far back as that body and stretching much 

 farther forward, as far forward in fact as does the lateral ventricle ; 

 but it is important to remember that it is divided into two 

 masses or nuclei, which are fused together and that imperfectly 

 at the very front only. These two nuclei are, the one the comma 

 shaped nucleus caudatus the bulk of which is placed forward 

 projecting into the lateral ventricle, and which on the whole is 

 the more dorsal portion of the whole body, the other the 

 irregularly shaped nucleus lenticularis the bulk of which is 

 placed farther back than the lateral ventricle, by the side of the 

 optic thalamus, and which on the whole is the more ventral 

 portion of the whole body. It is no less important to remember 

 that the radiating fibres, which we call the internal capsule, pass 

 in the hinder region of the whole body between the thalamus 

 and the nucleus lenticularis, forming the hind limb of the capsule, 

 and in the front region between the nucleus caudatus and the 

 nucleus lenticularis forming the front limb of the capsule, the 

 front and hind limbs being bent on each other so as to form an 

 angle, the so-called knee. 



628. The optic thalamus as a whole is a somewhat oval 

 mass of grey matter, lying as we have said athwart the diverging 

 crus, in which it is partly imbedded. Its curved median side 

 covered with a thin layer of central grey matter forms the lateral 

 wall of the third ventricle (Figs. 115, 116, 121), and in a longi- 

 tudinal vertical section of the brain taken in the line of the middle 

 of the third ventricle (Fig. 120, O.T.) is seen occupying the space 

 between the fornix and hind end (splenium) of the corpus callosum 



