460 TOPOGRAPHICAL ANATOMY. 



mater ; it is extended like a bridge across all the depressions, and 

 over all the sulci of the brain. 



III. Pia mater, slightly attached to the free surface of the brain, 

 and entering into all its sulci, depressions and cavities, it closes the 

 fourth ventricle at the fissur. transv. cerebelli, [abnormally] and 

 the third ventricle even at the foram. Bichat. in the Jiss. transv. 

 cerebri. 



709. IV. Cerebrum, great brain. Its superior convex surface 

 looks towards the cranial vault, and is divided into two hemispheres 

 by the 



Scissura longitudinalis, which penetrates as far as corpus cal- 

 losum, in front, before the genu corpor. callosi, and between the 

 anterior cerebral lobes to the base of the skull ; behind, posterior 

 to splenium corp. callosum, and between the posterior cerebral 

 lobes to the cerebellum, and receives thefalx cerebri. 



Anterior cerebral lobes. Their inferior surfaces lie upon the 

 fossa cranii anterior ; their internal surfaces meet together ; be- 

 hind they are separated from the middle lobes by the fossa Sylvii. 

 On the inferior surface, towards their inner border, the sulcus trac- 

 tus olfactorii is seen, at the posterior termination of which, close 

 before substantia per/or, media, lie the corp. mammillaria. 



Middle cerebral lobes are indistinctly bounded behind by margo 

 petrosus of petrous bone, and they occupy the fosses cranii medice. 



Posterior cerebral lobes occupy the space in the fossa occipitales 

 superiores. Between them and the cerebellum the Jissura transv. 

 cerebri leads to splen. corp. callos., corp. quadrigem., ventricul. 

 3., and later ales. 



710. V. Cerebellum, lesser brain, fills up the fossa occipitales 

 inferiores, is divided by the horse-shoe-shaped incisur a poster., at 

 the posterior border and falx cerebelli, into two hemispheres, by a 

 deep transverse groove,, sulcus horizontalis Reilii, into a superior 

 and inferior half, united in the middle line by the vermis [proc. 

 vermiformis]. The vallecula on the inferior surface of the vermis 

 receives anteriorly the pons Varolii, behind the medulla oblongata. 

 Between the last and the cerebellum the Jissura transversa cere- 

 belli leads into the fourth ventricle. The superior surface of the 

 cerebellum is separated from the posterior lobes of the cerebrum 

 by the tentorium. 



711. VI. Basis encephali. We find in the middle line from 

 behind to before, 



