THE SKELETON. 33 



posterior condyloid, opens more dorsally at the side of the 

 condyle. The former transmits the twelfth (hypoglossal)^ 

 cranial nerve, supplying the larynx, hyoid bone, and tongue. 

 The jugular foramen, or foramen lacerum posterius, is at 

 the juncture of the bulla, exoccipital, and basioccipital. 

 The internal jugular vein and the ninth, tenth, and eleventh 

 nerves pass through it. The basioccipital portion of this 

 bone lies entirely on the ventral aspect of the skull. It 

 articulates craniad with the basisphenoid by a suture which 

 is generally obliterated in cats three or four years old. 



The sphenoid bone lies in the center of the base of the 

 skull. It is composed of eight parts, corresponding to eight 

 distinct bones in the lower vertebrates: the basisphenoid, 

 articulating caudad with the basioccipital ; two alisphenoids, 

 extending dorsad from the basisphenoid and articulating 

 caudad with the temporals (Figs. 17 and 18) two ptery- 

 goids, projecting ventrally from the basisphenoid and 

 terminating in sharp processes; a presphenoid in the mid- 

 ventral line craniad of the basisphenoid; two orbitosphen- 

 oids, extending dorso-laterally from the presphenoid and 

 articulating craniad with the frontals. In an old cat, the 

 sutures between these eight parts become more or less oblit- 

 erated. The basisphenoid together with the alisphenoids 

 is sometimes called the posterior sphenoid in distinction to 

 the anterior sphenoid, composed of the presphenoid and 

 orbitosphenoids. 



The basisphenoid presents on its dorsal or cerebral sur- 

 face the sella turcica, or pituitary fossa, which lodges the 

 pituitary body of the brain (Fig. 9$). The posterior 

 boundary of this fossa is the clinoid plate, and its lateral 



ovale; p, presphenoid; pi, palatine; pi, pterygoid; pn, promontory 

 of the petrous ; po, postorbital process ; pr, premolar teeth ; pm, 

 premaxillary ; rd, fenestra rotundum; rt, foramen rotundum; st, 

 stapes ; sg, squamosal ; sf, stylomastoid foramen ; if, carotid 

 foramen, or foramen lacerum medius ; vm, vomer, forming the 

 septum between the posterior nares ; sg, zygornatic process of 

 squamosal. 



