THE SKULL. 223- 



along the inner wall of the orbit, close to its 

 dorsal border, to the foramen by which the 

 two nerves leave the orbit : this is situated 

 at the antero-superior angle of the orbit, and 

 has already been seen on the dorsal surface 

 of the skull. 



0. The articular surface for the hyo-mandibular car- 

 tilage is a concave depression on the side of the 

 hinder end of the skull, below the auditory cap- 

 sule. 



d. The post-orbital groove is a deep horizontal groove 



immediately above the articular surface for the 

 hyo-mandibular cartilage, and overhung by the 

 projecting ledge of the auditory capsule which 

 lodges the horizontal semicircular canal : it lodges 

 during life the venous canal through which the 

 orbital sinus communicates with the anterior 

 cardinal sinus. 



The anterior end of the groove is bridged over 

 by stout ligamentous tissue. 



e. The foramen for the glosso-pharyngeal nerve is at 



the hinder end of the floor of the post-orbital 

 ' groove, behind and below the horizontal semi- 

 circular canal of the ear. 



4. The ventral surface of the skull. 



a. The base of the skull is a broad flat plate of 



cartilage, crossed almost transversely a little 

 behind its middle by a pair of grooves in which 

 the carotid arteries lie. At the point of meeting 

 of the grooves in the middle line is an aperture 

 through- which the internal carotid artery enters 

 the skull. 



b. The apertures of the olfactory capsules are large, 



but are considerably reduced by the nasal car- 

 tilages, which are liable to be torn in cleaning 



