374 ZOOTOMY. 



included a space answering to the fifth ventricle of the 

 higher mammalia, but evidently a portion of the space 

 between the right and left hemispheres. 1 



LX. Trace the course of the hippocampus major by 



carefully cutting away the outer part of the temporal 



lobe : note : 



506. The descending cornu of the lateral ventricle, 

 exposed by the removal of the outer wall of the temporal 

 lobe ; it passes first almost directly outwards, then down- 

 wards, and finally inwards and forwards. The hippo- 

 campus major is continued the whole distance along its 

 inner wall. 



507. The posterior pillar of the fornix (Fig. 71, B, 

 p.fo\ a flat white band forming the projecting anterior edge 

 of the hippocampus major, and continued with the latter 

 into the descending cornu. Anteriorly it becomes con- 

 nected with its fellow of the opposite side just behind the 

 septum lucidum, forming the body of the fornix. 



508. The tsenia semicircularis (t.s\ a thin band of 

 white matter, just in front of the posterior pillar of the 

 fornix, and forming a sort of bed for the choroid plexus. 



509. The fissure of Bichat, a slit-like space between 

 the taenia semicircularis and the posterior pillar of the 

 fornix ; it leads on to the under surface of the brain, 

 between the anterior and inner edge of the temporal lobe 

 and the optic tract. 



LXI. Make a transverse incision through the body of 

 the fornix, immediately over the foramen of 



1 In the higher mammalia, e.g. man, the reptum lucidum becomes 

 very thin and translucent, whence its name, and, the anterior germ of 

 the corpus callosum being very \\ ell developed, and turning round the 

 anterior edge of the septum lucidum, the latter takes on the form of a 

 double membrane, situated between the corpus callosum above and in 

 front, and the body of the fornix ( 507) behind. 



