vi.] GENERAL VIE W OF INTERNAL SKELE TON. 227 



14. The cranial characters presented by man may be 

 indicated in the following generalized manner : 



The skull may be said to consist of a central axis (formed 

 by the basi-occipital and basi-sphenoid), to which ascending 

 and descending arches are annexed, and in which certain 

 structures are intercalated. 



We have the occipital arch, and in front of this a second 

 arch formed by the great alae of the sphenoid and the parietals, 



FIG. 197. IDEAL, GENERALIZED DIAGRAM OF AN OSSEOUS SKULL. 



a, ali-sphenoid ; ar, articulare ; bh, basi-hyal ; bo, basi-occipital ; bs, basi-sphe- 

 noid ; cb, cerato-branchial ; ch, cerato-hyal ; cpt, ecto-pterygoid ; d, dentary ; 

 eb, epi-branchial ; eh, epi-hyal ; eo, ex-occipital ; ep, epiotic ; ept, ento-ptery- 

 goid ;f, frontal ;fo, fenestra ovalis ;f 2 , fenestra rotunda ; g, quadrato-jugal ; 

 gh, glosso-hyal ; fib, hypo-branchial ; Ic, lachrymal ; le, lateral-ethmoid ; nt, 

 maxilla ; ma, malar ; me, median-ethmoid ; mpt, meta-pterygoid ; , nasal : op, 

 opisthotic ; os, orbito-sphenoid ; p, parietal ; pa, para-sphenoid; pb, pharyngo- 



branchial ;pf, post-frontal ;//, palatine \pm, pre-maxilla \ps, pre-sphenoid ://, 

 pterygoid ; ptc, pterotic; px, hyo-mandibular ; q, quadratum ; sh, stylo-hyal ; so, 

 supra-occipital; sph, sphenotic; sf 1 , squamosal ; sq 2 , pre-operculum ; t, ostrans- 

 versum ; th, tympano-hyal ; v, vomer ; 2 1 , upper zygoma; 2 a , lower zygoma. 



and, again in front, a third arch formed by the orbital alae and 

 the frontal. 



Into the median gap bounded by the arch of the frontal, 

 the olfactory organ (the ethmoid) is, as it were, thrust. 



Into the gap left on each side between the lateral occipital 

 and the great ala of the sphenoid, the auditory organ (the 

 temporal bone) is thrust. 



Similarly, the much smaller lateral gap left between the 

 great ala and the orbital wing of the sphenoid is related to 

 the organ of sight, which, though not ossified in man, like 

 Q 2 



