54 THE SKELETON OF THE CAT. 



pterygoid fossa and separated from it by a sharp ridge is the 

 small narrow internal pterygoid fossa (s\ which extends ven- 

 trad without interruption on to the surface of the hamulus (/) 

 and caudad to within two or three millimeters of the tympanic 

 bulla. From it the internal pterygoid muscle takes origin. 

 The hamulus (/) projects caudoventrad in this region, forming 

 a prominent feature in a lateral view. 



Four foramina leading into the cranial cavity are visible in 

 a lateral view of the skull, craniad of the tympanic bulla. The 

 one nearest the bulla is the foramen ovale (u) for the third 

 division of the fifth nerve ; next craniad of this is the foramen 

 rotundum (V) for the second division of the fifth nerve. These 

 two foramina pierce the alisphenoid : just craniad. of them, 

 between the alisphenoid and the orbitosphenoid, is the large 

 orbital fissure (r) (foramen lacerum anterius), which transmits 

 the third, fourth, and sixth cranial nerves and the first division 

 of the fifth. Dorsocraniad of the orbital fissure is the optic 

 foramen (w], for the optic nerve. 



Ventrad of the cranial portion of the orbit is the large 

 sphenopalatine foramen (g), for the nerves and arteries of the 

 same name. Just craniad of this is the small caudal opening 

 of the posterior palatine canal, which passes through the sub- 

 stance of the palatine bone and opens on its ventral surface 

 near its cranial margin. Just dorsad of the cranial root of the 

 zygomatic arch is the opening of the lachrymal canal (x), 

 while the root of the arch is pierced by the large infraorbital 

 foramen (j/), which transmits the infraorbital nerves and artery 

 from the orbit. 



The teeth (13-18), implanted along the alveolar border of the 

 maxillary and premaxillary, form a prominent feature in a 

 lateral view : they are described in the account of the alimen- 

 tary canal. 



The ventral surface of the skull (Fig. 41) is very complex. 

 It is separated by the orbits into a caudal and a cranial portion, 

 united by a narrow median trough-like part. Laterad of this 

 trough-like part are visible parts of the orbit and the zygomatic 

 arches, which do not properly belong to the ventral surface and 

 have already been described. 



