Chap, in.] CRANIAL CONTENTS. 37 



indicates in its anterior part the supramarginal 

 convolution, filling up the most prominent part of 

 the parietal eminence, and in its posterior part the 

 angular gyrus. 



Temporo-sphenoidal lobe. Bounded above by the 

 line of the Sylvian fissure, below by the upper 

 border of the zygoma, and a line continued back from 

 that border to a point midway between the occipital 

 protuberance and the posterior border of the mastoid 

 at its root G. The anterior end of the lobe reaches as 

 far as the posterior superior border of the malar bone. 

 Its posterior end is bounded by a line (slightly convex 

 backwards) drawn from the posterior end of the 

 Sylvian fissure to the point G. A line running 

 parallel with the Sylvian line, and one inch below it, 

 will indicate the first temporo-sphenoidal sulcus, and 

 another pai'allel line, three-quarters of an inch below 

 again, will mark the second temporo-sphenoidal sulcus. 

 The superior, middle, and inferior temporo-sphenoidal 

 convolutions will thus be mapped out. 



The occipital lobe occupies the remaining sur- 

 face of the scalp, being bounded below by the inner 

 half of the superior curved line, and in front by the 

 parieto-occipital sulcus and the temporo-sphenoidal 

 lobe. 



The cortical centres of tlie brain. A know- 

 ledge of the position of these centres is most impor- 

 tant in enabling certain brain lesions to be localised, 

 and in guiding the surgeon in opei-ations upon the 

 cerebral cortex. The precise area of each centre has 

 not yet been very accurately defined, and the exact 

 limits of each area are still in some details indefinite 

 It must be borne in mind also that one area fuses 

 with another. The following account is based mainly 

 upon that given by Dr. Gowers. 



The lower limb. The posterior part of the 

 superior frontal convolution, the upper parts of the 



