DISSECTING MANUAL. 



which joins the ala of the vomer; just external to this union 

 is the orifice of a canal (pterygo-palatine) which runs between 

 the vaginal process and the sphenoidal process of the palate 

 bone. [163] 



The posterior nares open into the nasal fossae; they are 

 quadrilateral and separated by the vomer. They are bounded 

 below by the horizontal plates of the palate bones, at the 

 sides by the internal pterygoid plates, and above by the vag- 

 inal processes of the sphenoid externally and the alse of the 

 vomer internally. [163] 



The zygomatic fossae (see page 9) lie external to the ptery- 

 goid processes; each extends between the malar and superior 

 maxilla in front, and the zygomatic process and its anterior root 

 at the side and behind. The spheno-maxillary fissure separates 

 the roof and anterior wall. Between the great wing of the 

 sphenoid and petrous temporal is a narrow cleft (spheno- 

 petrosal fissure) which is closed by a synchondrosis; this forms 

 a groove, for the cartilaginous part of the Eustachian tube, 

 which runs from the root of the internal pterygoid plate to the 

 inner side of the base of the alar spine, and there enters an 

 osseous canal, in the petrous bone, leading to the tympanum. 

 An osseous partition (cochleariform process) divides the canal 

 into an upper portion for the Tensor tympani, and a lower 

 part for the osseous part of the Eustachian tube. Just in front 

 of the alar spine is a small foramen (spinosum) ; in front of this 

 is a larger one (foramen ovale). [164] 



The basi-occipital (basilar part of the occipital) extends from 

 the body of the sphenoid to the foramen magnum; at its cen- 

 tre is an elevation (pharyngeal tubercle) from which a ridge 

 curves outward and backward on each side. Between the 

 front part of the basi-occipital, the root of the pterygoid proc- 

 ess, and the apex of the petrous temporal is an irregular open- 

 ing (foramen lacerum medium) whose lower part is occupied 

 by fibro-cartilage. Into this the Vidian canal opens anteriorly ; 

 and the carotid canal postero-externally, lying in the apex of 



[12] 



