THE NERVOUS SYSTEM. 



G19 



round the corpus callosum, and swelling out at its hinder and upper end 

 into the quadrate lobule (prascuneus), which is continuous with the 

 superior parietal lobule on the external surface. Marginal convolution 

 runs parallel to the preceding, and occupies the space between it and 

 the edge of the longitudinal fissure. The two convolutions are separated 

 by the calloso-marginal fissure. The internal perpendicular fissure is well 

 marked, and runs downward to its junction with the calcarine fissure : 

 the wedge-shaped mass intervening between these two is termed the 

 cuneus. The calcarine fissure corresponds to the projection into the pos- 

 terior cornu of the lateral ventricle, termed the Hippocampus minor. 

 The temporal lobe on its internal aspect is seen to end in a hook (unci- 

 nate gyrus). The notch round which it curves is continued up and 

 back as the dentate or hippocampal sulcus: this fissure underlies the 



Sulo. 

 tremus 



Fig, 872. Right hemisphere, from within. (After Eberstaller.) 



projection of the hippocampus major within the brain. There are three 

 internal temporo-occipital convolutions, of which the superior and infe- 

 rior ones are usually well marked, the middle one generally less so. 



The collateral fissure (corresponding to the eminentia collateralis) 

 forms the lower boundary of the superior temporo-occipital convolution. 



All the above details will be found indicated in the diagrams (figs. 

 371, 372). 



/Structure. The cerebrum is constructed like the other chief di- 

 visions of the cerebro-spinal system, of gray and white matter; and, a? 

 in the case of the Cerebellum (and unlike the spinal cord and medulla 

 oblongata) the gray matter (cortex) is external, and forms a capsule or 

 covering for the white substance. For the evident purpose of increasing 

 its amount without undue occupation cf space, the gray matter is vari- 

 ously infolded so as to form the cerebral convolutions. 



