440 THE BRAIN 



is still in position, should now be still further pared away, so as 

 to bring the subjacent septum pellucidum and the fornix more 

 fully into view. 



Upon the portion of the temporal lobe which has been separ- 

 ated, the dissector should examine again the fascia denlata, 

 which was mentioned on p. 414, and which is now much more 

 accessible. 



Fascia Dentata Hippocampi. The fascia dentata is 

 the free edge of grey matter which is placed between the 

 fimbria and the deep part of the upper surface of the hippo- 

 campal gyrus. The groove between it and the fimbria 

 is termed \hz fimbrio-dentate sulcus. The margin of the fascia 

 is notched, and its surface is scored with numerous closely- 

 placed vertical grooves. It begins posteriorly, in the region 

 of the splenium of the corpus callosum, as the fasciola cinerea 

 (Fig. 173), and it runs forwards into the cleft of the uncus, 

 from which it emerges again in the form of a delicate band, 

 called the cauda fascia dentatce^ which crosses the recurved 

 part of the uncus in a transverse direction. The cauda is 

 not always easily seen. 



SEPTUM PELLUCIDUM FORNIX TELA CHORIOIDEA 

 VENTRICULI TERTII. 



Septum Pellucidum. The septum pellucidum is a thin 

 vertical partition which intervenes between the anterior 

 cornua and the anterior parts of the central portions of the 

 two lateral ventricles (Fig. 164). It occupies the triangular 

 interval between the corpus callosum and the body and 

 columns of the fornix, being attached, above and anteriorly, 

 to the corpus callosum, and below and posteriorly, to the fornix. 

 It consists of two thin laminae which form the side walls of a 

 median cleft called the cavum septi pellucidi (Figs. 164, 174). 



Dissection. The narrow median strip of the corpus callosum, 

 posterior to the genu, should now be removed. Cut it trans- 

 versely across, and, gently raising it, separate the upper edge 

 of the septum pellucidum from its lower surface. Posterior to 

 the septum pellucidum the under surface of the median part of 

 the corpus callosum will be found to lie upon and to be con- 

 nected with the upper surface of the fornix. Sever that con- 

 nection also. The left half of the forceps major should be 

 preserved, so that its connection with the occipital lobe may be 

 more fully made out later. Snip off the upper edge of the 

 septum pellucidum with the scissors, in order to demonstrate 

 the two laminae with the interposed cleft. 



