THE BRAIX AXD ITS MEMBRAXES. 



779 



Wilder) a short distance behind the superior extremity of the furrow of Rolando. 

 It separates the marginal convolution from the gyrus fornicatus or convolution of 

 the corpus callosum (limbic lobe). 



The parieto-occipital fissure (internal parieto-occipital} is the continuation of 

 the fissure of the same name seen on the outer surface of the hemisphere. It 

 extends in an oblique direction downward and forward to join the calcarine 

 fissure on a level with the hinder end of the corpus callosum. It separates the 

 quadrate from the cuneate lobe. 



The calcarine fissure commences, usually by two branches, at the back of the 

 hemisphere, runs nearly horizontally forward, and is joined by the parieto-occipital 

 fissure, and continues nearly as far as the posterior extremity of the corpus callosum, 

 to terminate a little below the level of this commissure. It separates the cuneate 



Pulv. of 



optic thai. 



\ 



Cbrp. quad. 



Subst. nigra 



FIG. 469. Mesial or inner aspect of left hemisphere, together with optic thalamus and part of mid-brain. 

 The temporal lobe is drawn downward and backward away from the optic thalamus. The septum lucidum 

 is removed. 'Henle.) 



lobe from the fifth temporal or infracalcarine gyrus, and causes the prominence in 

 the posterior cornu known as the hippocampus minor or calcar avis, whence its name. 



The collateral fissure (fourth temporal sulcus) is situated below the preceding, 

 being separated from it by the infracalcarine gyrus. It runs forward, from the 

 posterior extremity of the brain, nearly as far as the commencement of the fissure 

 of Sylvius. It runs, at first, between the fourth temporal (below) and infracalcarine 

 (above) convolutions, and then lies beneath the hippocampal gyrus. It lies below 

 the posterior and middle horn of the lateral ventricle, and causes the prominence in 

 the latter known as the eminentia collateralis. 



The dentate or hippocampal fissure commences immediately below the posterior 

 extremity of the corpus callosum, and runs forward to terminate at the recurved 

 part of the hippocampal gyrus. It corresponds with the prominence of the hippo- 

 campus major in the descending horn of the lateral ventricle. 



The lobes or convolutions seen on the internal surface of the hemisphere are 

 as follows : gyfiu fonticatiu, iimrnimiL 'iii<i<lr<it>\ atm-atr, hippocampal, uncinate, 

 .'///, , i !',,(,. fourth temporal, and th>/ paracentral lolntJ' . 



The gyrus fornicatus, or convolution of the corpus callosum, is a well-marked 



