THE NERVOUS SYSTEM. 



123 



into the quadrate lobule (praecuneus), 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 inter- 

 vening between these two is termed the cuneus. The calcarine fissure 

 corresponds to the projection into the posterior cornu of the lateral ven- 

 tricle, termed the Hippocampus minor. The temporo-sphenoidal lobe on 

 its internal aspect is seen to end in a hook (uncinate gyrus). The notch 

 round which it curves is continued up and back as the dentate or hippo- 



FIG. 334. View of the right hemisphere in the median aspect (semi-diagrammatic). CC, corpus 

 callosum longitudinally divided; Gf , gyrus fornicatus; H, gyrus hippocampi; h,sulcus hippocampi; 

 U, uncinate gyrus: cm, calloso-margmal fissure ; Fl, median aspect of first frontal convolution; c, 

 terminal portion of sulcus centralis (fissure of Rolando) ; A, ascending frontal ; B, ascending parietal 

 convolution; PI', prsecuneus; Oz, cuneus; po, parieto-occipital fissure; o, sulcus occipitalis transver- 

 sus; oc, calcarine fissure; oc', superior; oc", inferior ramus of the same; D, gyrus descendens; T4, 

 gyrus occipito-temporalis lateralis (lobulus f usiformis) ; T5, gyrus occipito-temporalis medialis (lobulus 

 hngualis). (Ecker.) 



campal sulcus; this fissure underlies the projection of the hippocampus 

 major within the brain. There are three internal temporo -occipital con- 

 volutions, of which the superior and inferior 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 (Fig. 332, 333, 334). 



Structure. The cortical grey matter of the brain consists of five 

 layers (Meynert) (Fig. 335). 



1. Superficial layer with abundance of neuroglia and a few small multi- 

 polar ganglion-cells. 2. A large number of closely packed small ganglion- 

 cells of pyramidal shape. 3. The most important layer, and the thickest 

 of all : it contains many large pyramidal ganglion-cells, each with a process 

 running off from the apex vertically toward the free surface, and lateral 

 processes at the base which are always branched. Also a median process 



