Human anatomy, including structure and development and practical considerations . ate wall of the dentinal tubules is formed by a delicate membrane,the sheath of Neumann, which in appropriate transverse sections appears as a con-centric ring. On softening the decalcified dentine by acids or alkalies, the sheathsmay be isolated, since they resist the action of the reagents which attack the sur-rounding intertubular substance. The sheaths of Neumann are formed through theagency and at the expense of the dentinal fibres, the latter being smaller in old thanin young dentine. The sheaths, therefore
Human anatomy, including structure and development and practical considerations . ate wall of the dentinal tubules is formed by a delicate membrane,the sheath of Neumann, which in appropriate transverse sections appears as a con-centric ring. On softening the decalcified dentine by acids or alkalies, the sheathsmay be isolated, since they resist the action of the reagents which attack the sur-rounding intertubular substance. The sheaths of Neumann are formed through theagency and at the expense of the dentinal fibres, the latter being smaller in old thanin young dentine. The sheaths, therefore, may be regarded as specialized parts ofthe intertubular matrix, distinguished by less complete calcification and greaterdensity. The intertubular ground-substance of dentine resembles that of bone in beingcomposed of bundles of extremely delicate fibrillae of fibrous connective tissue. Thelatter, best seen in decalcified tissue, swell on treatment with water containing acidsor alkalies, and yield gelatin after prolonged boiling. The disposition of the bundles Dentinaltubules. Ground-section of dried tooth including afijacent enamel ?- 300. and dentine. 1552 HUMAN ANATOMY. of tibrilke—more regular in dentine than in bone—is longitudinal and parallel to theprimary surfaces of the dentine. In addition to the filires which extend lengthwise,others run oblicjuely crosswise in the layers of dentine. The bundles of fibrillaemeasure from . mm. in diameter, and aj)pear in transverse sections as smallpunctatetl fields. The tibrilke are knit together by the calcified organic matrix, inwhich the lime salts are deijosited in the form of spherules, the interstices betweenwhich are later tilled and calcification thus completed. When, as often happens, thelatter process is imperfect, irregular clefts, the iutcrirlobular spaces, remain, the con-tours of which are formed by the spheres or dentinal globules of calcare<jus interglobular spaces are of irregular form an
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