SKITLL (Icel. skid, bowl. cup; connected with AS. scale, Eng. scale, bowl. dish of a balance, and with AS. sccalu, sceole, 0I1G. scala. Ger, &hale, husk, scale, Goth. skaija. tile, OChurch Slay. skolika, mussel, Lith. skelti, to split). The bony framework of the head. It is divided into two parts, the cranium and the face. In human anat omy it is customary to describe the former as consisting of S and the latter of 14 bones: the 8 cranial bones, which constitute the brain-case, being the occipital, two parietal, frontal, two temporal, sphenoid, and cthmoid; while the 14 facial bones are the two nasal, two superior max illary, two lachrymal, two molar, two palate, two inferior turlanatcd, comer. and inferior max illary. The hones of the ear, the teeth, and the Wormian bones are not included in this enumera tion. At a very early period of foetal existence the cerebrum is inclosed in a membranous cap sule external to the dura mater and in close contact with it. This is the first rudiment of the skull, the cerebral portion of which is conse quently formed before there is any indication of a facial part. Soon, however, four or five proc esses jut from it on each side of the mesial line, which grow downward, incline toward each other, and unite to form a series of inverted arches, from which the face is ultimately devel oped. imperfect development or ossification of
these rudimentary parts of the face gives rise to the peculiarities known as harelip (q.v.) and cleft-palate, or in extreme eases to the form of monstrosity termed cyclops, in which, from ab sence of the frontal processes, the two orbits form a single cavity. and the eyes are more or less blended in the mesial line. See MONSTROS ITY.
The following is a brief summary of the suc cession of events that occur in the ordinary or normal development of the skull. Cartilage is formed at the base of the membranous capsule, which has been already described as thrown round the brain and capable of enlarging with it. This is speedily followed by the deposition of osseous matter at various points of the cap sule, which soon becomes converted into flakes of bone, which afford protection for the brain, while the intervening portions, which remain membranous, permit the skull to expand as its contents enlarge. The formation of these bony flakes on the convexity of the cranium is soon followed by the ap pearance of osse ous nuclei in the cartilage at the base, corresponding to the future oc cipital and sphe noid bones. Lastly, the various bones, some originating in membrane and some in cartilage (see