. Text-book of embryology. Embryology. iks C. A, ^ft)A^ Fig. 162.—Diagram illustrating tooth succession in an Elasmobranch (A, primitive, B, existing condition) ; an Amphibian (C) ; anil a Reptile {Lacerla) (D). , dental groove ; , dental lamina ; , placoid scale ; t, tooth. Enamel is present as a thin layer towards the point of the fang: traced towards the base it passes into a simple fine cuticle-like basal membrane. Succession of Teeth.—In cases where the teeth have become restricted to special areas, and more particularly in cases where from their shape and from the habits of thei
. Text-book of embryology. Embryology. iks C. A, ^ft)A^ Fig. 162.—Diagram illustrating tooth succession in an Elasmobranch (A, primitive, B, existing condition) ; an Amphibian (C) ; anil a Reptile {Lacerla) (D). , dental groove ; , dental lamina ; , placoid scale ; t, tooth. Enamel is present as a thin layer towards the point of the fang: traced towards the base it passes into a simple fine cuticle-like basal membrane. Succession of Teeth.—In cases where the teeth have become restricted to special areas, and more particularly in cases where from their shape and from the habits of their owner they are liable to be broken off or damaged by wear or otherwise, it is usual to find a special arrangement for the replacement of the lost or injured teeth by new ones. Such an arrangement is seen in its simplest form in an ordinary Dog-fish or Shark (Fig. 162, A and B). The portion of skin—ectoderm with its strong and fibrous underlying dermis—to which the tooth-bases are attached is gradually, by processes of differential growth, caused to shift its position in an outward direc- tion over the edge of the jaw which supports it. This is brought about by the skin undergoing a continual slow process of absorption or atrophy along the outer margin of the jaw (about the point. Please note that these images are extracted from scanned page images that may have been digitally enhanced for readability - coloration and appearance of these illustrations may not perfectly resemble the original MacBride, E. W. (Ernest William), 1866-1940; Kerr, John Graham, 1869-; Heape, Walter, 1855-1929. London : Macmillan
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Keywords: ., bookcentury1900, bookdecade1910, bookpubli, booksubjectembryology
