210 A MANUAL OF ANATOMY. 



These fibres are grouped in four bundles, one beneath 

 each gyrus fornicatus tcznicz tectce and one on either 

 side of the median line the stria longitudinales ; between 

 the latter a thin groove is left called the raphe. 



The longitudinal fibres start from the base of the brain, 

 at the beginning of the fissure of Sylvius, and pass forward 

 to the corpus callosum (as its peduncles), over which they 

 continue to the forceps major. 



The taeniae tectae are stray fibres belonging to the gyrus 

 fornicatus. 



The Lateral Ventricles. Figs. 30, 31, 32, 35, 41 to 49 

 inclusive. 



These are the irregular cavities which are contained with- 

 in the cerebral hemispheres. 



Each lateral ventricle communicates with the third ven- 

 tricle and with each other through the foramina of Mon- 

 ro. A lateral ventricle presents, in horizontal section, a 

 central portion, an anterior, a posterior, and a middle pro- 

 longation or horn. The anterior horn curves forward, 

 downward, and outward, the posterior horn curves back- 

 ward and inward, and the middle horn takes a course 

 backward, outward, downward, forward, and inward (the 

 descending horn). 



All these prolongations open into the body of the ven- 

 tricle, which is that portion of the ventricle extending from 

 the foramen of Monro to the beginning of the descending 

 and posterior horns, and corresponds to the intraventricular 

 portion of the optic thalamus. 



The Boundaries of the Ventricle. The anterior horn, 

 body, and posterior horn are roofed over by the arched 

 corpus callosum as previously described. The internal wall 

 of the anterior horn is formed by the septum lucidum ; of 



