Cerebrum. 10V 



nter. 



Uorpus 

 quadrigem. 



. 448. The Third Ventricle, laid open. 



View from above, natural size. 



After removing the Tola choroidea superior (s. Velum interpositum), 

 and pushing apart the inner surfaces of both optic thalami, the third 

 ventricle, Ventriculus medius s. tertius is laid open to view. It is bounded 

 by six walls : an upper, the Tela choroidea superior ; two lateral, the 

 inner surfaces of both optic thalami a lower, corresponding to the 

 middle of the base of the brain ; an anterior, formed by the anterior 

 pillars of the fornix, and a posterior, formed by the Corpus quadri- 

 geminum. The lateral walls are connected by three commissures; the 

 anterior commissure, Commissure* anterior, in front of the anterior 

 crura of the fornix, the posterior commissure, Commissura poste- 

 rior^ in front of the Corpus quadrigeminum , and the middle com- 

 missure, Commissura media s. mollis, which connects the grey portions 

 of the inner surfaces of both optic thalami (sometimes wanting). 



Beneath the anterior commissure is the Iter s. Aditus ad infundibulum, 

 and beneath the posterior commissure, the Aditus ad aquaeductum Sylvii, 

 which latter, situated below the Corpus quadrigeminum, connects the third 

 and fourth ventricles. 



Heitzmann, Atlas. II. 15 



