. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. TEETH. 889 the turgescent duct with which it is in con- tact, the tubes which proceed to the surface d, while maintaining their normal relation of the right angle to it, are extremely short; and the layer of dentine separating the poison- tube from the pulp-cavity is proportionally thin. The calcigerous tubes that radiate from the opposite side of the pulp-cavity to the exposed surface b of the tooth are dispropor- tionally long. The teeth of Ophidians are developed and completed in that part which forms the ori- ginal s
. The cyclopædia of anatomy and physiology. Anatomy; Physiology; Zoology. TEETH. 889 the turgescent duct with which it is in con- tact, the tubes which proceed to the surface d, while maintaining their normal relation of the right angle to it, are extremely short; and the layer of dentine separating the poison- tube from the pulp-cavity is proportionally thin. The calcigerous tubes that radiate from the opposite side of the pulp-cavity to the exposed surface b of the tooth are dispropor- tionally long. The teeth of Ophidians are developed and completed in that part which forms the ori- ginal seat of the tooth-germs in all animals ; viz. the mucous membrane or gum covering, the alveolar border of the dentigerous bones. This germ presents the same lax tissue, and is as abundantly developed, as in the Pike, Lophius, and many other fishes; in which it likewise serves as the nidus and locality for the complete development of the teeth. The primitive dental papillae in the common harm- less snake very soon sinks into the substance of the gum, and becomes inclosed by a cap- sule. As soon as the deposition of the cal- careous salts commences in the apex of the papilla the capsule covering that part becomes ossified and adherent to the dentine, and the tooth begins to pierce and emerge from the gum before its mould, the pulp, is half com- pleted. Fresh layers of cells are successively added to the base of the pulp, and converted, by their confluence and calcification, into the tubular dentine, until the full size of the tooth is attained, when its situation in the gum is gradually changed, and its base becomes surface of the pulp ; and the base of the groove of the loose, growing, poison-fang is brought into the same relation with the duct of the poison gland as the displaced fang, which has been severed from the duct. Saurians.— The existing species of lizards differ from those of the crocodile in the anchy- losed condition of the teeth, which present few modifications o
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