758 



THE NERVOUS SYSTEM. 



corpus striatum (caudate nucleus), tcenia semicircularis, optic thalamus, clwroid 

 plexus, one-half of body of for nix, and corresponding posterior pillar. 



The anterior cornu is deep and 



narrow, 



frontal 



Oenu of the 



corpus 



callosum 



passing outward into the 

 lobe and curving round the 

 anterior extremity of the corpus stri- 

 atum. Its apex points outward. It 

 is bounded, above, by the corpus cal- 

 losum ; externally, by the corpus stri- 

 atum (head of caudate nucleus) ; in 

 front, by the posterior surface of the 

 genu of the corpus callosum ; inter- 

 nally, by the anterior or broad por- 

 tion of the septum lucidurn ; infe- 

 riorly, by the upper surface of the 

 rostrum (each side of its middle line) 

 of the corpus callosum. This last is 

 the floor of the cornu, and is exceed- 

 ingly narrow, the outer Avail, convex 

 toward the cavity, almost meeting the 

 lower part of the septum lucidurn be- 

 low (Figs. 448 and 449). 



The posterior cornu, or digital cav- 

 ity (Fig. 445), curves backward into 

 the substance of the occipital lobe, 

 its direction being backward and out- 

 ward, and then inward. On its inner 

 wall is seen a longitudinal eminence 

 which is produced by the extension 

 inward of the calcarine sulcus ; this is 

 called the hippocampus minor, or cal- 

 car avis. Just above this is a smaller 

 projection, bulb of the posterior horn 

 (Fig. 456), caused by the bulging of the fibres of the forceps major of the corpus 

 callosum. 



Between the middle and posterior 

 horns a smooth triangular surface is 

 observed. It is called the trigonum 

 ventriculi. 



The middle or descending cornu, 

 the longest of the three (Fig. 445), 

 traverses the temporal lobe of the 

 brain, forming in its course a remark- 

 able curve round the back of the optic 

 thalamus (pulvinar}. It passes, at 

 first, backward, outward, and down- 

 ward, and then curves round the 

 crusta forward and inward, nearly 

 to the apex of the middle lobe, close 

 to the fissure of Sylvius. Its upper 

 boundary, or roof, is formed by the 

 under surface of the corpus callosum, 

 the small portion of the pulvinar of 

 the optic thalamus covered by epithe- 

 lium, and by the white matter (internal capsule) of the temporal lobe, with which 

 are incorporated the reflected parts of the nucleus caudatus of the corpus striatum 

 and tsenia semicircularis, which are prolonged into it. Its lower boundary, or 



Anterior 

 cornu 



Nucleus 

 caudatus 



Sept. luc. 



Ant. pillars oj 

 thefornix 



(ext. 

 Capsule < 



(int. 



Claustnm, 

 Optic thalam. 



Lenticular 

 nucleus 



Svlenium of 

 the corp. 

 callosum 



Post, part 

 of the . 

 nucleus 

 caudatus 



Post, cornu 



FIG. 448. -Horizontal section of the right half of the 

 cerebrum, X 2. putaraen. a, b, and c nuclei of the 

 optic thalamus. (Gegenbaur.) 



Corpus 

 callosun, 



Sept. 

 pellucid 



Claustrum 



FIG. 449. Transverse vertical section < 

 spheres through the anterior eornua, X 

 face looks forward. (Gegenbaur.) 



f the hcmi- 

 The cut sur- 



