THE CEREBROSPINAL NERVOUS SYSTEM. 



505 



line in the interior of the brain is laid open, called the lateral ventricles. 

 They are separated by a thin double partition, the septum lucidum, be- 

 tween the laminas of which is an interval containing fluid, the fifth ven- 

 tricle; they communicate by an aperture below. They are lined with 

 ciliated epithelium. Each ventricle consists of a narrow interval extend- 

 ing into the anterior and posterior regions from the middle region of 

 the corresponding hemisphere. Its middle portion or body is straight, 

 but each horn is more or less curved. In the floor of the cavity project 

 portions of the chief basal ganglia, the corpus striatum in front, and the 

 optic thalamus behind, and a white band of fibres, the tasnia semicircu- 

 laris, between them. For the relation of the other portions of the interior 



FIG. 345. View of the Corpus Callosum from above. %. The upper surface of the corpus cal- 

 losura has been fully exposed by separating the cerebral hemispheres and throwing them to the 

 side; the gyrus fornicatus has been detached, and the transverse fibres of the corpus callosum 

 traced for some distance into the cerebral medullary substance. 1, the upper surface of the corpus 

 callosum; 2, median furrow orraphe; 3, longitudinal striae bounding the furrow; 4, swelling formed 

 by the transverse bands as they pass into the cerebrum; 5, anterior extremity or knee of the cor- 

 pus callosum; 6, posterior extremity; 7, anterior, and 8, posterior part of the mass of fibres pro- 

 ceeding from the corpus callosum; 9, margin of the swelling; 10, anterior part of the convolution 

 of the corpus callosum; 11, hem or band of union of this convolution; ls>, internal convolutions 

 of the parietal lobe; 13, upper surface of the cerebellum. (Sappey after Foville.) 



of the brain including those of the arched white commissure or fornix 

 which extends backwards from the septum lucidum, and consists of two 

 lateral halves joined only in the middle, with two anterior pillars and 

 two posterior crura and of the third ventricle, refer to Fig. 342 and the 

 description. 



The Internal Surface (Fig. 347) contains the following gyri and 

 sulci: 



