1388 



A MANUAL OF ANATOMY 



orbital gyrus is external to the outer limb of the orbital sulcus. 

 The anterior orbital gyrus is situated in front of the transverse limb 

 of the orbital sulcus. The posterior orbital gyrus Hes behind the 

 transverse limb of the orbital sulcus. 



Internal Surface of the Frontal Lobe. — ^The internal or mesial 

 surface presents only one convolution, namely, the marginal 

 gyrus, which is situated between the supero-mesial border of the 

 hemisphere and the calloso-marginal sulcus. It is continuous with 

 the superior frontal gyrus, and anteriorly is broken up by one or 

 two sulci. Its posterior part is almost completely detached, and 

 forms the paracentral lobule, which contains the upper end of the 

 fissure of Rolando. 



Corpus Callosum 



Anterior Pillar of Fornix 

 Septum Lucidum 



Pineal Body, 

 Splenium ^ 



Gena passing into 

 Rostrua 



V oramen 

 of Monro 



-^ Anterior Commissure 



Optic Thai, and Mid. Com. 

 Optic Nerve 

 Pkuitary Body 

 Tuber Cinereum 

 Corpus Albicans 



Cerebellum 



Fourth Ventricle 



Third Nerve 

 ' Pons Varolii 

 Crus Cerebri 

 /A Aqueduct of Sylvius 

 Medulla Oblongaai 



Fig. 584. — The Mesial Surface of the Left Cerebral Hemisphere 



{HiRSCHFELD AND LF.VEILLlfe). 



Parietal Lobe. — This lobe lies between the large frontal and small 

 occipital lobes, and above the temporal lobe. It is bounded an- 

 teriorly by the fissure of Rolando, which separates it from the frontal 

 lobe. Posteriorly it is bounded by (i) the external part of the 

 parieto-occipital fissure, and (2) a line drawn across the external 

 surface of the hemisphere from the extremity of this fissure towards 

 the pre-occipital notch on the infero-lateral border of the hemisphere, 

 from i^ to 2 inches in front of the occipital pole. 



The parietal lobe has two surfaces — external and intemaL 



