248 



TIIB ANATOMY OF THE HOBSK 



tions of the postero-superior and postero-inferior lobes, it is directed forwards at the base 

 of the brain (Plate 33, Hipp, con.), between the crus cerebri and the outer olfactory 

 tract. Finally, it terminates in the nipple-like eminence already noticed {Unc. con.). 



The whole of this great convolution corresponds very closely to the gyrus fornicatus of 

 human anatomy. Thus, the part which turns round the genu and rests on the upper 

 surface of the corpus coUosum is the callosal convolution ; the part from the splenium 

 to the side of the cerebral crus is the hippocampal convolution; and the nipple-like 

 eminence is the uncinate convolution. 



The hippocampal part of the gyrus fornicatus has a small process which projects 

 forwards under the splenium ; and as the convolution cui'ves forwards to emerge at the 

 side of the crus, it rests on the optic thalamus. By carefully raising the convolution from 

 the thalamus, there will be brought into view a fissure on the under aspect of the former. 

 This is the hippocampal fissure, and it projects the convolution into the lateral ventricle 

 as the hippocampus. Beyond this fissure the edge of the hiijpocampus is seen, margined 

 by a thin-edged white band — the taenia hippocampi. The hippocampus and its taenia 

 here form the upper boundary of the great transverse fissure of the brain, by which the 

 pia mater of the hemisphere projects towards the interior of the cerebrum as the vduni 

 interpositum. 



Fl6. 31. 



Corpus Callosum and Ikner Face of the Cerebral Hemisphere. 



1, 2. Right and left cerebral hemispheres ; 3. Cerebellnm ; C. Corpus callosum ; G. F. Gyrus 

 fornicatus (its caUosal portion) ; C. M. Calloso-marginal fissure ; A. M. Antero-marginal convolu- 

 tion ; P. M. Postero-marginal convolution. 



Directions. — With a large, thin-bladed, sharp knife a horizontal slice 

 should be removed from the top of one or both cerebral hemispheres, 

 down to the level of the corpus callosum. 



The hemisphere will now be seen to contain both grey and white 

 matter. In the centre of the hemisphere the white matter forms a large 

 mass connected with that of the opposite side by the corpus callosum. 

 At the surface the mass sends a white core into each convolution. The 



