THE THIRD VENTRICLE. 



765 



This space communicates in front with each lateral ventricle ^^ ^^ 

 through the foramen of Monro ; and behind is a passage beneath ventricles. 



- r 



-77. VIEW OK THE THIRD AND FOURTH VENTRICLES : THE FORMER 

 BEING EXPOSED BY THE REMOVAL OF THE VELUM INTERPOSITUM J AND THE 

 LATTER BY DIVIDING THK CEREBELLUM VERTICALLY IN THE MlDDLE LlNE. 

 THE THIRD VENTRICLE is THE INTERVAL IN THE MIDDLE LINE BETWEEN 

 THE OPTIC THALAMI. 



a. Caudate nucleus. 



b. Optic thalaraus. 



c. Anterior commissure, seen be- 

 tween the anterior pillars of the 

 fornix. 



d. Middle or soft commissure. 



e. Posterior commissure. 

 /. Pineal stria. 



y. Pineal l>ody. 



h and /. Corpora quadrigemina. 



The fourth ventricle, n, is on the 



posterior surface of the medulla 

 oblongata. 



k. Valve of Vieussens. 



I. Upper peduncle of the cere- 

 bellum. 



o. Fasciculus teres. 



p. Superior fovea. 



r. Inferior fovea. 



s. Clava. 



4. Fourth nerve arising from the 

 valve of Vieussens. 



the corpora quadrigemina into the fourth ventricle, which is named 

 the aqueduct of Sylvius. In the floor, in front, there is a 



