. Cuvier's animal kingdom : arranged according to its organization. Animals. IGO AVES. of Birds is formed ; the enormous volume of air contained in the air-cavities contri- butes to the strength of this voice, and the trachea, by its various forms and move- ments, to its intonations. The upper larynx, which is extremely simple, has little to do with it. The face, or upper mandible of Birds, formed principally by the intermaxillaries, is prolonged backwards into two arcades, the internal of which is composed by the pala- tine and pterygoid bones, the external by the maxiUaries and jugals, and w
. Cuvier's animal kingdom : arranged according to its organization. Animals. IGO AVES. of Birds is formed ; the enormous volume of air contained in the air-cavities contri- butes to the strength of this voice, and the trachea, by its various forms and move- ments, to its intonations. The upper larynx, which is extremely simple, has little to do with it. The face, or upper mandible of Birds, formed principally by the intermaxillaries, is prolonged backwards into two arcades, the internal of which is composed by the pala- tine and pterygoid bones, the external by the maxiUaries and jugals, and which are both supported on a moveable tympanic bone, commonly termed the square bone {os carré), that represents the drum of the ear : above, this same face is articulated or united to the skull by elastic laminae ; a mode of union which always leaves some mobility. The homy substance which invests the two mandibles supplies the place of teeth, and is occasionally serrated, so as to represent them.* Its form, as also that of the mandibles which support it, varies excessively, according to the sort of food resorted to. The digestion of Birds is in proportion to the energy of their vitaUty, and the amount of respiration. The stomach is composed of three parts : the craw, which is an expansion of the gullet ; the proventriculus, a membranous stomach, furnished in the thickness of its coats with a multitude of glands [variously disposed and shaped in different groups], the secretion of which humects the aliment ; and lastly, the gizzard, armed vnth two powerful muscles united by two radiating tendons, and inter- nally lined by a coating of cartilage. The food is more readily ground there, as Birds are in the habit of swallowing small stones to augment its triturating power. In the greater number of species which subsist only on flesh or fish, the muscles and the internal lining of the gizzard are reduced to extreme tenuity, so that it appears to make but one sac with the proventri
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Keywords: ., bookcentury1800, bookdecade1840, bookpublishe, booksubjectanimals
