THE TELENCEPHALON. 



1157 



strise, represent an atrophic convolution, the gyrus supracallosus. Traced forward 

 and around the recurved genu and rostrum, the mesial stria is prolonged into the 

 gyrus siibcallosiis, a small crescentic cortical tract on the mesial surface of the 

 hemisphere immediately below the rostrum (Fig. 994); while the lateral stria is 

 continued into the area parolfactoria (page 1153) and into the anterior perforated 

 space. When followed backward and around the splenium, the striae and gray 

 matter of the corpus callosum become continuous with the gyrus dentatus and, by 

 way of the latter, with the uncus. 



The under surface of the corpus callosum (Fig. 998) exhibits a very 

 evident transverse striation and forms the roof of the anterior cornu and body of 

 both lateral ventricles. With the exception of a strip of varying width along the 

 mesial plane, where attached to the septum lucidum in front and to the triangular 



Fig. 997. 



Frontal pole 



Genni 



Mesial longitudinal 

 St rise 



Upper surface 

 of corpus callosum 



Lateral longitudinal 

 stria 



Forceps anterior 



Transverse fibres 



Tapetuin 



Forceps posterior 



Splenium 



Occipital pole 



Cerebral hemispheres from which upper and median parts have been removed to expose corpus callosum ; on left 

 side longitudinal striae and thin layer of gray matter cover upper surface of corpus callosum ; on right side these 

 have been scraped away to expose transverse fibres and anterior and posterior forceps. 



body of the fornix behind, the corpus callosum is free and covered with the 

 ependyma which lines the ventricular spaces. In consequence of the bridge being 

 shorter than the length of the hemispheres, from most parts of which it receives 

 fibres, the latter are consolidated at the ends of the corpus callosum and give rise to 

 the genu and the splenium. On gaining the lateral margins of the corpus callosum, 

 its fibres are no longer restrained but radiate in all directions (radiatio corporis cal- 

 losi) towards the cortex and intersect the fibres of the corona radiata (page 11 86). 

 Those traversing the thinner body and upper part of the splenium of the com- 

 missure pass laterally and in each hemisphere from a thin but definite fibre-sheet, 

 known as the tapetum, which extends over the lateral ventricle, especially its 

 posterior horn, and constitutes the lateral wall of its posterior cornu and of the 

 adjacent part of the descending horn. The fibres composing the fore-part of the 

 genu turn forward as a distinct band, the forceps anterior, towards the frontal 



