THE EOHM-BBLATIONS OF THE HUMAN BEAIN. 



193 



another, as has been done in the preparation shown in. Pig. 129, the island 

 lies in full view. The island is then seen to be divided into two small lobules 

 by means of a deep fissure, the sulcus centralis insulce, which passes obliquely 

 iipward and backward from below and in front. Several, almost perpendicu- 

 lar, sulci divide the anterior broader lobule into three or four gyri breves 

 insulsB. The posterior lobule is really nothing but a single, longer gyrus: 

 the gyrus longus. It borders directly on the temporal lobe. An important 

 fissure, the sulcus centralis or central fissure, begins in the operculum, and 

 ascends from there to the median edge of the hemisphere, which it frequently 

 incises. At the bottom of this fissure a small annectant gyrus not infre- 

 quently divides it into a superior and inferior portion. Recent surgical 



Fig. 130. — Lateral aspect of the brain. The gyri and lobuli are designated by 

 Roman letters, the sulci and fissurte by italics. 



operations, as well as the knowledge gained from physiological studies, have 

 made it desirable to divide the fissure in parts. The two genua, the superior 

 genu and the inferior genu of the central sulcus, respectively indicated in 

 the diagram by an asterisk, serve as such points of division. Locate the 

 fissure in Fig. 130. This central sulcus separates the loius frontalis from 

 the lohus parietalis. All that lies below the Sylvian fissure is called the 

 lobus temporalis. In front of the sulcus centralis lies the anterior central 

 gyrus,^ behind it the posterior central gyrus} The region in front of the 



^ Circonvolution frontale ascendente of the French writers. 

 ^ Circonvolution pariStale ascendente of the French writers. 



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