18 A MANUAL OF ANATOMY. 



The inion ; this is another name for the external occipital 

 protuberance. 



Laterally. The supra-orbital arch is the prominent 

 margin bounding the orbital cavity above. It terminates 

 internally at the extremity of the nasofrontal groove in 

 the obscure internal angular process, and externally in the 

 prominent external angular process (E. A. P.), which is 

 one of the very useful cranial landmarks. 



The zygomatic arch lies horizontally and limits the 

 cranial from the facial regions. It also corresponds very 

 nearly with the lower and external border of the temporal 

 lobe of the brain. 



The external auditory meatus is a conspicuous and 

 useful landmark used in cranial measurements, as it is both 

 easily felt and seen. 



The parietal eminence is more of an area than a point, 

 but it is useful in taking general measurements. 



The mastoid process (its tip and posterior border), 

 is a prominent and stable landmark in the adult, but in 

 children cannot be of much use as it is not developed. 



The superior curved line of the occipital bone forms 

 usually a readily recognizable ridge arching forward from 

 the inion to the base of the mastoid process. It determines 

 the boundary between the back of the head and neck. 



The " Sylvian point " is the point upon the cranium 

 which indicates where the Sylvian fissure reaches the ex- 

 terior of the cerebrum. 



It is found at a distance of one and one-quarter inches 

 directly behind the external angular process of the frontal 

 bone. 



Relations of the exterior of the brain to the surface 

 of the cranium. 



The margins of the cerebral hemispheres. 



