286 



THE NERVOUS SYSTEM 



visible from the surface, but lies deep within the Sylvian 

 fissure, which divides the frontal from the temporal lobe, 

 and is concealed by the convolutions of the upper lobes 



Fissure of^ 

 Rolando ~~ 



^.-Parietal Lobe 



V"^>. Occipito-parietal 



^ X / Fissure 



Frontal Lobe 



Occipital Lobe 

 ^Sylvian Fissui 

 Temporal Lobe 



Fig. 131. Side view of the left cerebral hemisphere. 



(Fig. 132). Other principal fissures are the deep lon- 

 gitudinal one separating the hemispheres ; the fissure of 

 Rolando, which lies between the frontal and parietal 



lobes ; and the occipito- 

 parietal fissure, separat- 

 ing the parietal from 

 the occipital lobe. A 

 broad band of white 

 nerve fibers, the corpus 

 callosum, connects the 

 two hemispheres (Fig. 

 129). In the base of 

 - each frontal lobe is a 

 bulbous expansion of gray and white matter connected 

 by a stalk, or peduncle, called the olfactory tract, with the 

 mass of the hemisphere. These are the olfactory bulbs, 



Fig. 132. Side view of brain with tem- 

 poral lobe cut away so as to expose 

 the underlying insula. 



