Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 116 VERTEBRATA. skull* is developed partly by ossifications in the cartilaginous capsule or by ossifications proceeding from the membranous peri- chondrium; partly by the addition of membrane bones, which gradually supplant the cartilaginous parts. Segmentation of the skull.—It is only when the cranial capsule is bony that any comparison can be instituted between the arrangement of the hard parts of the skull and that of the parts of a vertebra : this comparison has led to the view that
Elementary text-book of zoology (1884) Elementary text-book of zoology elementarytextbo0201clau Year: 1884 116 VERTEBRATA. skull* is developed partly by ossifications in the cartilaginous capsule or by ossifications proceeding from the membranous peri- chondrium; partly by the addition of membrane bones, which gradually supplant the cartilaginous parts. Segmentation of the skull.—It is only when the cranial capsule is bony that any comparison can be instituted between the arrangement of the hard parts of the skull and that of the parts of a vertebra : this comparison has led to the view that the skull is composed of three or four vertebra? or segments. These are from behind forwards, the occipital, parietal, frontal and ethmoid segments. Each such segment, according to the vertebral theory of (P. Frank) Goethe and Ql FIG. 574.—Lateral view of a goat's skull ; O/, exoccipital bone; C, condyle ; Os, supra- occipital; Sq, squamosal; Ty, tympanic; Pe, petrosal; Pm, paramastoicl process; Pa, parietal; Fr, frontal, Lti, lachrymal ; -ZV«, nasal; Fo, optic foramen ; MX, maxilla; Jiux, inter-maxilla (pre-maxilla) ; Jn, jugal; Pa/, palatine ; Ft, pterygoicl. Oken, is supposed to consist of a basal part corresponding to the body of the vertebra, and of a neural arch formed of two lateral pieces and a median dorsal piece (spinous process) (fig. 574). According to this theory the basi-occipital bone would correspond to the body of the vertebra, the two exoccipitals to the lateral parts of the neural arch, and the supra-Occipital to the dorsal median parts or spinous process. The bones of the middle or parietal region of the skull consist of a basal bone, the, basisphenoid, two lateral bones, the alisphenoids and two dorsal bones, the parietals; the two latter are membrane bones, and complete the arch dorsally. The bones of the * Compare especially Eeichert and Kolliker. Huxley, Parker etc.
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