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Show 114 ON •rHE VEHTEBR.ATE SKULTJ. Perhaps no method of investigating the stru ture of the skul1 con d uces s0 much towards th. e attainment uf a dear understan d1. ng. of t]11·s sort of arclntoctur.a l anaton1y, as th. o stud y of sec t1.0 11 s, made (a; long plan s winch have a defimte relation to the principal axes of the skull. Fig. 47. • • • • ·y k ]] F· F. tal Pa Parietal. S.O. Fig. 47.-DJagrammattc s1de vtew of a human ·u .- 1 • qon · · . . d lateral Supra-occipital. S.01• Squama occip_itis above the tm·culal' lferophtl~ ;~ Mast(lid sinuses. .As. Alisphenoid. Sq. Portw squamosa of the ~empoi al bon~ N 1 L. process and pars mastoidea. Ty. Tympanic. St. 'tyloitl proc~~~· .:n ~s:ndible. Lachrymal. .Ju. Jugal, or Malar. Pmx. Premaxilla .. Mx. Maxi a. ·. nification Jfy. Hyoid. m. Malleus. i. incus. [These letters w1ll bear the same slg throughout the series of figures of crania.] TilE STRUCTURE OF THE HUMAN SKULL. 115 If a vertical and transverse soetion be taken through the cranium, in snch a manner that tho plane of th section shall traverse both external auditory meatu. os, the skull will be eli vi dod into two nnoqual portions-an anterior, larger, and n posterior, smaller. Tho former, if viewed from behind) ·will present the appearance represented in ] ig. 48. Fig. 4-8. Fig. 48.-Anterior half of the sknll ot a young person (six or seven years of age) tran - versely bisect€'tl. The temporal bone ( Tt) on each ide is left in outline, and the contour of the alisphenoid is supposecl to be seen through it.:.._[f, optic foramina between the roots of the orbito-sph€>noids; v; j01·anum ovate for the third division of the trigem~nal; N indicates the nasal chamber; llf:'C is pla(·ecl in the buccal chamber. A stout n1edian floor (BS) whence lateral continuations (AS) are prolonged to meet an arched roof (Pa), divides a capacious upper chamber, which, during life, lodged a part of the brain, from a lower chamber, formed by the bones of tho face. Thi. lower chamber itself j agmn separable into two I 2 |
