THE PKKEIiUAL HEMISPHERES. 159 



(Osborne), situated above the foregoing nucleus in the posterior and 

 middle portions of the hemispheres ; (3) the upper internal cell-area 

 (Osborne) is the area of large cells in the dorsal part of the inner 

 wall j (4) the Corpus striation (Osborne) is a mass of cells between 

 the corpus callosum and the cotitmisstira anterior; Koppen doubts 

 the correctness of Osborne's opinion, and suggests that a group of 

 cells found in the wall of the third ventricle in front of ' Meynert's 

 band ' may perhaps be a corpus stria f urn. 



From a transverse section through one of the cerebral hemispheres ; from Stieda. 

 (Magnified 360 times.) 



a Epithelium of lateral ventricle. 



6 Nerve cells. 



c Connective-tissue processes from the Pia mater. 



A bundle of longitudinal medullated nerve-fibres, the ' round 

 bundle/ is found on either side of the median line (Fig. 107 d), 

 and near the lower border in the posterior portion of this region ; 

 these fibres can be traced from the posterior section of the thala- 

 meneephalon ; they diminish in number as they course through the 

 base of the cerebral hemispheres, and are ultimately lost in the 

 lower anterior part of the outer walls. A. second strand of lon- 

 gitudinal fibres is the continuation of that of the Tnler-cinereum 

 above described, which can be followed to the outer wall of the 

 posterior part of the ventricles, and to the anterior commissure. 



The commissures are : (i) The corpus callow m, a large bundle of 

 transverse fibres, seen best in a transverse section, at the point of 

 junction between the lamina terminalis and the cerebral hemi- 

 spheres, forming an arch over the roof of the anterior prolongation 

 of the third ventricle. The fibres course to the inner and anterior 

 parts of the hemispheres, and are situated chiefly behind the fo- 

 ramen Monroi. To this commissure must be added those fibres 

 which unite the two olfactory lobes, and possibly the fibres (Co//i- 

 missiira posterior] found in the roof of the third ventricle (Koppen). 

 (2) The Commiuura anterior (Stieda), a smaller set, found immedi- 



