1156 



HUMAN ANATOMY. 



prolonged into the sharply recurved and tapering rostrum, whose thin edge is 

 continued backward and downward into the lamina cinerea, the attenuated anterior 

 wall of the third ventricle (page 1132). The rounded and massive posterior end of 

 the corpus callosum, known as the splenium, overlies the pineal body and the 

 superior colliculi, and above bounds the cleft through which the pia mater gains 

 the velum interpositum (page 1162). 



The convex upper surface of the corpus callosum, where it forms the bottom of 

 the longitudinal fissure, is free, except behind where in contact with the posterior 

 part of the falx cerebri ; laterally it is partially overlaid by the callosal gyrus, which, 



FIG. 996. 



Opening of cere- 

 bral vein 



Mesial surface of cere 

 bral hemisphere 



Lamina cine 



Optic chiasm, cut 



Inftmdlbutan. 



Pituitary body 

 Tulier ' 

 Interpedunc 



Mammillary body 

 Oculomo 

 Sphenoi 

 Cerebral 

 Pi 



Basilar artery 



Corpora quadrigemina 



Pon 



Aqueduct of Syl 

 Superior nn ' ' 



ueduct of Sylvius S SS , 

 i medullary velum '/S 

 Fourth ventricle'/ / 

 Choroida! plexus' / 

 Right vertebral artery 



Mesial section of brain in 



showing relations to skull and dura ; cerebral falx has been partly removed, 



arachnoid and pia arc still in place. 



however, is separated from it by tin- intervening ra/Av^ / ,v/^vo (sulcus o>rpui is callosi ). 

 Although consisting practically exclusively of transversely coursing nerve-til >res, 

 which produce a corresponding cros-, striation, the upper surface' of the corpus 

 callosum (Fig. 997; is covered by a thin atrophic layer of gray matter iiidusetim 

 Uii-ciim i which laterally is continuous with the cortical substance of the callosal 

 gyrus and contains rudimentary strands of longitudinal nerve-fibres. These are 

 arranged on each side of the slight groove marking the mid-line in two strands ; tin- 

 one, the stria medialis, is placed close to the strand of the opposite side and with 

 it constitutes the so-called nerves of Lonrisi. The other strand, the stria lateralis, 

 or tn-tiia l<-ct(t, lies farther outward and is covered by the overhanging callosal gyrus. 

 These rudimentary structures, including the thin sheet of gray matter and the two 



