292 



ANATOMY OF THE CENTRAL NEETOUS SYSTEM. 



The optic radiation has already entered its terminals in the section shown in 

 Pig. 185; we see it only as a gray area, in transverse section, in the midst of the 

 white medullary substance lateral to the ventricle. 



The section shown in Fig. 187 passes down Just in front of the posterior end 

 of the corpus eallosum. This very instructive section allows us to observe how the 

 tapetum of the corpus eallosum develops from the fibers of the splenium, and how 

 the tapetum envelops the posterior horn of the ventricle and covers the inner side 

 of the cornu Ammonis. A part of the hippocampal gyrus — a part that is atrophied, 

 it is true — still lies directly under the corpus eallosum in man. It is designated as 

 the fasciola einerea. The cornu Ammonis is here met with in its most posterior 



Gyrus cent. post. 



LDbnIus paraceat. 



l-obus pariet. sup. 

 Fiss. interpariet. 



L )t>iis pariet. inf. 



Cornu Aininonis 



Fiss. parieto-occip. 

 Gyrus lingualis 



G\Tus fusiform 



.\ 



ynis temp. med. 



'-/■ j I asc. long. inf. 



I Rfid occiinto- 

 I thalam. 

 'apetnm 



riis temp, inf. 



Fig. 188. 



position, just in front of the occipital lobe. The ventricle opens, on the one hand, 

 posteriorly into the posterior horn, and, on the other, ventrally into the inferior 

 horn. It is for this reason that it appears so long and wide. Outside of the optic 

 radiation lies the longitudinal bundle \\hieh passes from the occipital lobe into the 

 temporal lobe. In the most dorsal territory- the medulla still belongs to the radia- 

 tion from the uppermost portion of the two central gyri; then follows, farther 

 laterally and externally, the territory of the parietal lobe, and thereupon the medulla 

 of the gyrus angvilaris and the temporal g.\Ti. 



The section illustrated in Fig. 188 lies directly at the base of the euneate 

 occipital lobe, conseqiiently behind the end of the corpus eallosum. The ventricle, 



