. Handbook of anatomy; being a complete compend of anatomy, including the anatomy of the viscera a chapter on dental anatomy, numerous tables, and incorporating the newer nomenclature adopted by the German anatomical Society, generally designated the Basle nomenclature or BNA . s. Cementum.—This is a product of the osteoblasts (cemen-toblasts) of the periodontal (alveolo-dental) ligament. Theprocess is almost identical with the development of subperiostealbone. Cementum is distinguished by the unusual number of DENTAL ANATOMY. 417 transversely placed bundles of fibrillar—or Sharpeys
. Handbook of anatomy; being a complete compend of anatomy, including the anatomy of the viscera a chapter on dental anatomy, numerous tables, and incorporating the newer nomenclature adopted by the German anatomical Society, generally designated the Basle nomenclature or BNA . s. Cementum.—This is a product of the osteoblasts (cemen-toblasts) of the periodontal (alveolo-dental) ligament. Theprocess is almost identical with the development of subperiostealbone. Cementum is distinguished by the unusual number of DENTAL ANATOMY. 417 transversely placed bundles of fibrillar—or Sharpeys of these are imperfectly calcified. The cementum appearsfirst in the vicinity of the neck of the tooth and advancestowards the apex of the root as the radicular dentin is laveddown. The knowledge of root-fonnation is important. The extentof root-growth at various ages is graphically illustrated byFig. 152. The dental tissues are: (1) Xasmytlvs membrane, (?)enamel, (3) dentine, (4) cementum, (5) pulp. Nasmythsmembrane is a pellicle 9 to 18u. thick) covering the enamel, longpersisting, of high organic content, resistant to the action ofacids. It is two-layered: (1) outer, of cornified remnants ofenamel-organ; (2) inner, structureless, consisting of the last V*°« week embryo FKi. growth. formed, imperfectly calcified portion of the enamel is the hardest tissue of the human body (containing!»^ per cent, of inorganic salts). It consists of prisms (.^in diaMeter) running approximately at right angles to the ex-ternal surface of the tooth, in a slightly spiral course to thedentine. Between these prisms is a cementing substance. Inthe outer portions of the enamel, intercalated or accessoryprisms have been described. The margin of each enamel-rod isstraight and smooth, but may optically appear varicose, due tothe beaded nature of its more highly calcified central brown stria- of Retzius are pigment zones running in thegener
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