On the structure of teeth, and the resemblance of ivory to bone, as illustrated by microscopical examination of the teeth of man, and of various existing and extinct animals / by Professor Owen.

  • Owen, Richard, Sir, 1804-1892.
Date:
[1838?]
Catalogue details

Licence: Public Domain Mark

Credit: On the structure of teeth, and the resemblance of ivory to bone, as illustrated by microscopical examination of the teeth of man, and of various existing and extinct animals / by Professor Owen. Source: Wellcome Collection.

Provider: This material has been provided by The Royal College of Surgeons of England. The original may be consulted at The Royal College of Surgeons of England.

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    and are the centres from wliicli the true calcigerous tubes radiate, and they are, therefore, analogous to the simple pulp-canal of the human incisor, whicli, with its radiating microscopic calcigerous tubes, may be compared to a single medullary canal with its corresponding microsco- pic radiating tubes in the Hays, Orycteropiis, &c. Myliobatis.—A longitudinal section of a single dental plate, viewed by a low power of an inch focus, exhibits at its base a coarse network of large irregular canals, filled with a vascular medullary pulp. From this network smaller medullary canals proceed in a slightly-diverging course, subdividing dichotomously with interspaces equal to six or eight of their own diameters. In a transverse section of the tooth, seen under the same power, the area of the medullary canals is seen to present ge- nerally an elliptical form, from which radiating calcigerous tubes are faintly perceptible. Each canal and its series of tubes is surrounded by a line of generally an hexagonal form, and which constitutes the boundary between contiguous canals and tubes, the whole tooth being thus composed of an aggregate of simple elongated, commonly six-sided prismatic teeth, placed vertically to the grinding surface. A section through the roots of the tooth shows that these parts are occupied by a network of irregular canals, which anastomose by arched branches with the network of tlie contiguous root, and tliese with the network of coarser tubes which occupy the basis of the tooth for an extent ex- ceeding the length of the root itself. With a higher power, ^th inch focus, the calcigerous tubes are seen to radiate in all directions from the medullary canals, and are sent off throughout the whole course of the canal. The tubes are short, wavy, richly arborescent, and form numerous anastomoses with each other. The transverse sections of the tooth show that the area of each medul- lary canal has been filled up or diminished by the deposition of a series of concentric lamellae. The ramification of the tubes in this tooth presents the same general character as those of Acrodus, but they are shorter, and each grou]j in the transverse section is separated from the contiguous one by the re- gular boundary lines above-mentioned, which distinguish the teeth of the Myliobatis from those of the Acrodus, Psammodus, Cestracion, or any of the shark tribe. The tooth of the Orycteropus is that which has the nearest resemblance to the tooth of the Myliobatis. Acrodus nobilis.—The crushing teeth of this extinct genus are com- posed of two substances, viz. a thin external almost colourless layer, which represents the enamel, and an amber-coloured coarser ivory composing the body of the tooth, and continuous with and passing into the coarse cellular bony basis and support of the tooth. Microscopic sections of this tooth afford the most beautiful appearances, and, per- haps, the most instructive illustration of the relation of ivoi’y to bone. The body of the tooth consists of groups of beautifully branched and irregularly wavy medullary canals imbedded in a clear matrix. These canals are surrounded by concentric strata, and closely resemble the canals of Havers in true bone. The calcigerous tubes, which radiate from the medullary canals, have a graceful undulatory course and are