240 



THE NERVOUS SYSTEM 



pallium, from the rest of the temporal lobe, and is a very conspicuous fissure in 

 most mammalian brains (Fig. 83) . 



Convolutions. Dorsal to the corpus callosum is the gyrus cinguli between 

 the sulcus of the corpus callosum and the sulcus cinguli. The superior frontal 

 gyrus is continued over the dorsal border of the hemisphere from the dorso- 

 lateral surface and reaches the sulcus cinguli. Surrounding the end of the 

 central sulcus is a quadrilateral convolution, known as the paracentral lobule. 

 It is bounded by the sulcus cinguli, its marginal ramus and the paracentral 

 sulcus. Another quadrilateral area, known as the precuneus, is bounded by 

 the parieto-occipital fissure, the subparietal sulcus, and the marginal ramus of 

 the sulcus cinguli. The hippocampal gyrus lies between the hippocampal fissure 



Superior frontal gyrus 



Sulcus of corpus callosum ,- x 

 Gyrus cinguli -. 

 Sulcus cinguli -~,,^ 

 Corpus callosum-,,^ 

 Gyrus fornicatus - 

 Frontal lobe- 



Post. par olfactory sulcus -- 

 Parolfactory area- 



Ant, par olfactory sulcus''' 



Temporal lobe ' 



S. centralis 

 Paracentral sulcus 



Paracentral lobule 



- - Parietal lobe 

 *- Marginal ramus 

 __..-- Precuneus 



vV Subparietal sulcus 



^'\- - - Parieto-occipital fissure 



- Cuneus 



-- Calcarine fissure 



- Lingual gyrus 



, . Isthmus of gyrus 



fornicatus 

 " Hippocampal fissure 



Rhinal fissure ' 



Uncus ' Hippocampal gyrus J 



Inf. temporal gyrus 



Collateral fissure 

 Fusiform gyrus 



Inferior temporal sulcus 



Fig. 171. Diagram of the lobes, sulci, and gyri on the medial aspect of the human cerebral 



hemisphere. 



dorsally and the collateral and rhinal fissures ventrally. Its rostral extremity 

 bends around the hippocampal fissure to form the uncus. It is connected with 

 the gyrus cinguli by a narrow convolution, the isthmus of the gyrus fornicatus. 

 Under the name gyrus fornicatus it has been customary to include the gyrus 

 cinguli, isthmus, hippocampal gyrus, and uncus. Between the collateral fissure 

 and the inferior temporal sulcus is the fusiform gyrus which lies on the basal 

 surface of the temporal lobe in contact with the tentorium of the cerebellum 

 (Figs. 170, 172). 



It has been customary to apportion parts of the medial and basal surfaces 

 of the cerebral hemisphere to the frontal, parietal, occipital, and temporal 

 lobes, as indicated in Fig. 171. According to this scheme the gyrus fornicatus 



