326 NEUROLOGY, OR ANATOMY OF NERVOUS SYSTEM 



The anterior part of the corpus callosum forms in front a 

 bend, the genu, and this extends back along the base of the 

 brain up to the lamina cinerea as the rostrum. Here it sends 

 off the peduncles of the corpus callosum. Behind it forms a 

 thick border, the splenium, or pad. The under surface of the 

 corpus callosum is connected behind with the fornix and for 

 the rest of its extent with the septum lucidum. It forms the 

 roof of the lateral ventricles. 



The corpus callosum is a mass of transverse fibers seen on 

 separating the hemispheres of the cerebrum. It is best studied 

 from a view of a mesial section. The mass of radiating fibers 

 pass transversely, connecting almost every part of one cere- 

 bral hemisphere with the corresponding part of the other. 

 They radiate in various directions within the hemispheres, 

 and are divided into a pars frontalis, a pars parietalis, and a 

 pars occipi tails. 



A portion of the dorsal surface is free for a width of about 

 1 cm. on either side of the mesial plane, partly covered by the 

 indusium, and overlapped by the callosal gyres, a fold of pia 

 intervening. 



It is a long, thick, somewhat flattened arch of white, bend- 

 ing upon itself anteriorly to form the genu, while its posterior 

 extremity is rounded and somewhat folded to form the splenium. 

 The genu becomes reflected to form the rostrum, which ends 

 in a flattened portion called the cupola, which in turn joins 

 the lamina terminalis in front of the anterior commissure. 



The Lateral Ventricles 



The lateral ventricles are serous cavities, have a thin lining 

 membrane, covered by a layer of epithelium cells (epcndyma), 

 which secrete a serous fluid. They are contained one in each 

 hemisphere, separated by the septum lucidum, and each is 

 divided into a body and three cornua, an anterior, posterior, 

 and middle. The foramen of Monro connects them with the 

 third ventricle. 



The central cavity, or body, is roofed by the corpus callosum, 

 and in the floor, from without inward, are found the caudate 

 nucleus of the corpus striatum, tsenia semicircularis, part of 

 the optic thalamus, choroid plexus, and part of the fornix. 



