THE GRAY MATTER. 621 



a similar section taken nearer the middle line (Fig. 145) shows 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 shows that the globus pallidus, as well as the putamen, 

 becomes continuous with the nucleus caudatus. 



FIG. 142. 



Diagrammatic Outline of a Sagittal Section taken through the Right Hemisphere (Man), Seen 

 from the Mesial Surface. (Sherrington.) Half natural size. The plane of the section is not 

 truly sagittal, but slightly inclined. Nc, the caudate nucleus exposed to the left of the letters Nc 

 in nearly its entire anterior extent, to right of the letters in a considerable part of its posterior 

 extent. It forms an arch of gray matter over the gray matter of Pt, the putamen, and Gp, the 

 globus pallidus of the lenticular nucleus ; Na, the amygdaloid nucleus ; Oi, Ci, Ci, the internal 

 capsule ; Ca, the anterior commissure ; cc, the hinder limit of fibres of the splenium corporis 

 callosi, P, the parietal lobe ; T, the temporal. 



Thus, when we speak of the corpus striatum as a whole we mean a large 

 mass of gray matter lying lateral to the optic thalamus, reaching nearly as 

 far back as that body and stretching much further 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 im- 

 perfectly 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 further 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 cau- 

 datus 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. 



541. The optic thalamus as a whole is a somewhat oval mass of gray 



