THE CRANIAL CAVITY 



69 



of the base of the skull (Fig. 31). The hard palate (Palatum durum) is 

 concave from side to side, and in its length also in the anterior part. It 

 is formed by the palatine processes of the premaxillse and maxilla?, and the 

 horizontal parts of the palate Ijones. It is circumscribed in front and 

 laterally by the superior alveolar arch, in which the upper teeth are im- 

 planted. The interalveolar space (]Margo interalveolaris) is that part of the arch 

 in which alveoli are not present. Behind the last alveolus is the alveolar 

 tuberosity, and internal to this is a groove for the palatine vein. In the middle 

 line is the median palatine suture (Sutura palatina mediana). In the line of the 

 suture, a little behind the central incisors, is the foramen incisivum, through which 

 the palato-labial artery passes. On either side, parallel with the alveolar part of 

 the maxilla, is the palatine groove (Sulcus palatinus), which contains the palatine 

 vessels and nerve. It is con- 

 tinuous at the anterior pala- -2/ 

 tine foramen with the palatine 

 canal, which is situated be- 

 tween the maxilla and the pal- 

 ate bone. The palatine cleft 

 (Fissura palatina) is the nar- 

 row interval along the outer 

 margin of the palatine process 

 of the premaxilla; it is closed 

 in the fresli state by cartilage. 

 Scattered along each side of 

 the palate are several vascular 

 foramina. The transverse 

 palatine suture (Sutura pala- 

 tina transversa) is about half 

 an inch from the posterior bor- 

 der. The latter is in a plane 

 through the last molar teeth, 

 and is concave and free. 



The posterior or nuchal 

 surface (Norma occipitalis) is 

 formed by the occipital bone. 

 It is trapezoidal in outline, 

 wider below than above, con- 

 cave dorso-ventrally, convex 

 transversely. It is separated 

 from the superior surface by 

 the occipital crest, and from 



the lateral surfaces by the superior curved lines (Linese nuchse superiores). Below 

 the crest are two rough areas for the attachment of the complexus muscles. A little 

 lower is a central eminence on the sides of which the ligamentum nuchse is attached. 

 At the lowest part centrally is the foramen magnum, at which the brain and spinal 

 cord meet; this is bounded laterally by the occipital condyles, which are flanked by 

 the paramastoid or styloid processes (Processus jugulares). 



The apex of the skull is formed by the bodies of the premaxillse and mandible, 

 carrying the incisor teeth. 



Fig. 34. — Cr.\n'i.\l C.wity of Horse .\s Seen on Sagittal Sec- 

 tion OF Skull. 

 O, Frontal sinus; r, sphenoidal sinu.s; t, cerebral compartment 

 of cranium; 1-3, ridges (juga) corresponding to fissures of lateral 

 surface of cerebrum; 4, groove for middle cerebral artery; 5, en- 

 trance to for. lacerum orbitale; 6, entrance to optic foramen; 7, 8, 

 grooves on sphenoid bone; 9, incisura spinosa; 9', groove for middle 

 meningeal artery; 10, fossa for pyriform lobe of cerebrum; 11, 

 incisura ovalis; 12, incisura carotica; 13, internal auditory meatus; 

 14, foramen lacerum basis cranii; 15, hypoglossal foramen; 16, 

 petrous temporal; 17, orifice of a<iuaeductus vestibuli; 18, orifice 

 of aquaeductus cochleir; 19, foramen magnum; 20, petrosal crest; 

 21, two plates of frontal bone; 22, supraoccipital; 23, basioccipital; 

 24, tentorium osseum; 25, body of sphenoid. (After Ellenberger- 

 Baum, Top. Anat. d. Pferdes.) 



THE CRANIAL CAVITY 

 This cavity incloses the brain, with its membranes and vessels, 

 small and is ovoid in shape. 



It is relatively 



