THE NERVOUS SYSTEM 



1503 



point it ascends almost vertically towards the sagittal suture, lying 

 about I inch behind the coronal suture. 



The small posterior division of the middle meningeal artery hes 

 about 2 inches behind the anterior division. 



The Sylvian point coincides with the pterion, and is situated about 

 li inches behind the external angular process of the frontal bone, 

 and about 2 inches above the zygomatic arch. It indicates the 

 division of the stem of the fissure of Sylvius into its three limbs — 

 anterior, ascending, and posterior. The anterior limb of the fissure 



Fig. 624. — The Outer Surface of the Right Cerebral Hemisphere, 

 SHOWING the Relations of its Gyri and Fissures to the Exterior 

 OF the Cranium (from a Preparation made by the Author). 



passes horizontally forwards for about i inch, and the ascending 

 limb upwards and slightly forsvards for a variable distance, from 

 the Sylvian point. 



The pars orhitalis of the frontal lobe of the cerebrum lies helow 

 the anterior limb ; the pars triangularis of the frontal lobe is situated 

 between the anterior and ascending limbs ; and the pars basilaris of 

 the frontal lobe is situated directly behind the ascending limb. 



The pars triangularis of the left side {le cap of Br oca) is the seat of 

 the speech-centre. 



