PARTS SEEN IX THE LATERAL VENTRICLES. 



549 



upper and back part of the third ventricle. 

 canal of Bichat, is no longer admitted. 



The existence of this canal, named the 



The velum having been removed, the optic thalami are brought fully into 

 view, together with the cavity of the third ventricle situated between 

 them, while, behind the third ventricle, between it and the upper surface of 



375. 



Pig. 375. DISSECTION OF THE BRAIN FROM ABOVE, EXPOSING THE LATERAL, THIRD AND 

 FOURTH VENTRICLES, WITH THE SURROUNDING PARTS (from Hirschfeld and Leveille). 



a, the anterior part or knee of the corpus callosum divided ; its fibres are seen spreading 

 on each side into the cerebral hemispheres ; b, anterior part of the surface of the right 

 corpus striatum in the anterior cornu of the lateral ventricle ; b', the same on the left 

 side, in which the grey substance has been dissected so as to show the peduncular medul- 

 lary fibres spi-eading through the corpus striatum into the cerebral hemisphere ; c, points 

 by a line to the tzenia semicircularis : d, surface of the thalamus opticus ; e, the anterior 

 pillars of the fornix divided; below they are seen descending in front of the third ven- 

 tricle, and between them is seen a part of the anterior commissure ; above the letter 

 is seen the fifth ventricle represented as a slit between the two laminae of the septum 

 lucidum ;_/", placed on the soft or middle commissure ; g, in the posterior part of the third 

 ventricle; on either side of this letter is the v/hite stria or peduncle of the pineal gland ; 

 immediately below the letter is the small posterior commissure and the pineal gland ; h, 

 the upper, and t, the lower of the corpora quadrigemina ; k, processus a cerebello ad 

 cerebrum ; and close to this the valve of Vieussens, which is partly divided by a median 

 incision along with the middle lobe of the cerebellum, so as to open up the fourth ven- 

 tricle ; I, the hippocampus major and corpus fimbriatum separated from the posterior 

 pillar of the fornix and descending into the middle cornu of the lateral ventricle ; m, 

 posterior cornu of the lateral ventricle and hippocampus minor ; n, eminentia collateralis ; 

 o, the cavity of the fourth ventricle ; p, posterior surface of the medulla oblongata ; r, 

 section of the middle lobe showing the arbor vitse ; s, upper surface of the cerebellum 

 brought into view on the left side by the removal of a considerable part of the posterior 

 cerebral lobe. 



