272 



MAMMALIAN ANATOMY 



Fia. 195. 



however, few structural changes, only such as result from antero- 

 posterior compression. The anterior sphenoid is scarcely developed in 

 front of the optic foramina (Fig. 193), hence the great wings, the ali- 

 sphenoids, project beyond the anterior end of the body. The ptery- 

 goid processes, in place of projecting as thin plates forward under the 

 anterior sphenoid, are narrow and at right angles to the inferior sur- 

 face, and each is attached between the foramen rotundum and the fora- 

 men ovale, which are thereby widely separated. The posterior sphenoid 

 does not extend backward beyond the foramina ovalia, which thus pierce 

 the alisphenoids close to the posterior margin. The great wing exhibits 

 an important feature which is rudimentary in the great wing of the 

 cat's sphenoid. The vertical part of the alisphenoid of the cat presents 

 only intracranial and extracranial surfaces, and hence is linear in trans- 

 verse horizontal section ; in the 

 human alisphenoid this region of 

 the extracrauial surface is drawn 

 outward, along a line extending 

 downward parallel with the pos- 

 terior border, into a sharp malar 

 crest (Figs. 194, 195), which ar- 

 ticulates with a corresponding- 

 crest on the malar bone, and thus 

 separates the orbital cavity in 

 front from the temporal and 

 zygomatic fossae behind. The 

 extracranial surface is thereby 

 divided into a true orbital sur- 

 face, which faces forward and 

 inward, and a lateral surface, 

 which faces outward. In section 

 the vertical part of the great 



THE SKULL, SEEN PARTLY IN FRONT AND ON 

 THE RIGHT SIDE. 



1, frontal bone; 2, parietal bone; 3, temporal bone, 

 squamous portion ; 4, sphenoid bone, temporal sur- 

 face of its great wing ; 5, ethmoid bone, orbital sur- 

 face ; 6, maxilla ; 7, malar bone ; 8, lachrymal bone ; 9, 

 nasal bone ; 10, mandible ; a, orbital plate of the frontal 

 bone; b, temporal surface; c, orbital surface of the 

 large wing of the sphenoid bone ; d, mastoid portion 

 of the temporal bone ; e, orbital surface of the malar 

 bone ; /, orbital plate of the maxillary ; g, infraorbital 

 foramen ; h, mental foramen ; i, symphysis ; j, ramus ; 

 k, coronoid process; I, condyloid process; m, angle; 

 n, lachrymal fossa. 



wing is triangular. 



If the bone be now examined 

 in detail, the student will observe 

 that the anterior aspect of the 

 presphenoid is covered on each side of the ethmoidal (or sphenoidal) 

 crest by a thin pyramidal bone which exhibits an opening into the 

 corresponding sphenoidal sinus. This bone is the spheno-turbinal, 



