748 



Occipital 

 lobe. 



Temporal 

 lobe. 



DISSECTION OF THE BRAIN. 



convolutions are continuous with those of the occipital lobe behind, 

 and of the temporal lobe below. 



The occipital lobe is small, and triangular in shape. It is 

 separated from the parietal lobe for a short distance above by the 

 parieto-occipital fissure ( po} ; but its anterior boundary is for the 

 most part artificial, being constituted by the line just mentioned, 

 continuing the direction of that fissure across the outer surface of 

 the hemisphere. Its convolutions join those of the parietal and 

 temporal lobes. 



The temporal lobe projects into the -middle fossa of the base of 

 the skull. Its fore part is separated from the frontal and parietal 

 lobes by the fissure of Sylvius, but its hinder part is only limited 

 by the lines above mentioned, across which its convolutions pass 

 into those of the parietal and occipital lobes. 



Sulcus of Rolando. 



Pronto- parietal operculum. 



,'d i 

 Frontal operculum. -- "'' 



Temporal operculum. 

 Short gyri of the island. Central sulcus. 



FIG. 271. THE ISLAND OF REIL, SHOWING WHERE THE OPERCI'LA 

 HAVE BEEN CUT AWAY. 



Central 

 lobe, or 

 island of 

 Reil, 



surrounded 

 by three 

 sulciof Reil, 



Opercnla 

 of the 

 insula ; 



Other convolutions of this lobe will be seen on the under surface 

 of the hemisphere. 



The central lobe, insula, or island of Reil (fig. 271), is placed at 

 the bottom of the fissure of Sylvius, and is concealed by the over- 

 lapping of the temporal, parietal and frontal lobes. If the margins 

 of the Sylviaii fissure be drawn asunder, the island will be seen to 

 have a triangular form, with the apex directed downwards towards 

 the anterior perforated space, and to be bounded by three furrows 

 (the sulci of Reil), one in front, one above, and another behind ; the 

 hinder one being continuous with the posterior branch of the fissure 

 of Sylvius. The central lobe is placed opposite the lenticular 

 muscles of the corpus striatum in the interior of the hemisphere. 



The portions of the frontal, parietal and temporal lobes which 

 overhang, and conceal, the island are called opercula of the insula. 

 These opercula have been cut away to expose the island in fig. 271, 



