. An introduction to the osteology of the mammalia . icranial plate. (2.) A pair of bars forming the floor for the fore-brain,known as the trabeculae (tr); these are continued forwardfrom the parachordals. They meet behind and embrace thefront end of the notochord; and after separating for somedistance bend in again in such a way as to inclose thepituitary body (py). In front of this they coalesce, andtogether with the olfactory capsules (pi) give rise to the pre-sphenoidal and ethmoidal regions of the cranium (Fig. 47, I.). (3.) The cartilaginous capsules of the sense organs. Ofthese the audi
. An introduction to the osteology of the mammalia . icranial plate. (2.) A pair of bars forming the floor for the fore-brain,known as the trabeculae (tr); these are continued forwardfrom the parachordals. They meet behind and embrace thefront end of the notochord; and after separating for somedistance bend in again in such a way as to inclose thepituitary body (py). In front of this they coalesce, andtogether with the olfactory capsules (pi) give rise to the pre-sphenoidal and ethmoidal regions of the cranium (Fig. 47, I.). (3.) The cartilaginous capsules of the sense organs. Ofthese the auditory and olfactory capsules unite more or less 146 THE SKULL. [CHAP. intimately with the cranial walls. The basicranial plategrows up as an arch over the occipital region of the skull,and coalescing with the auditory capsules gives rise to theprimordial skeleton of the occipital, periotic, and basi-sphenoidal regions of the skull: the parietal and frontalregions being afterwards completed by ossification in mem-brane surrounding the cranial FIG. 51.—Elements of skull (seen from below) of an embryo Pig two-thirds of aninch long, parachordal cartilage; nc notochord ; an auditory capsule ; pypituitary body; tr trabeculse; trabecular cornu ; pn prenasal cartilage; enexternal nasal opening ; ol nasal capsule ; ° palatopterygoid tract inclosed inthe maxillopalatine process; mn mandibular arch; hy hyoid arch; firstbranchial arch ; -ja facial nerve ; Ba glossopharyngeal; 8£ vagus ; 9 hypoglossal. Besides the parts composing the cranium proper, theMammalian skull is completed by the labial cartilages, themeaning of which is still very obscure, and a series of threepaired descending cartilaginous bars or arches, developed inthe visceral laminae, constituting the sides of the face andneck. The first visceral (mandibular) arch divides itself intoa short proximal or dorsal, and a much longer distal orventral end (Meckels cartilage}. The first sends outforward
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Keywords: ., bookcentury1800, bookdecade1880, booksubjectbones, bookyear1885
