The Dental cosmos . portions of the dentine. This corroborates what Dr. Bodecker statedin 1878, and also more satisfactorily explains the clinical fact that atthis particular portion of a carious cavity in a tooth, the sensibility ismuch more acute than in other parts of the same tooth. In some instances the crown of the tooth may be nearly coveredwith a well-developed or a stratified and slightly pigmented enamel, CONGENITAL DEFECTS IN ENAMEL. 609 the other portions being coated with a thin layer highly pigmented,again denoting deficiency in lime-salts. (See Fig. 4.) We present here a transve
The Dental cosmos . portions of the dentine. This corroborates what Dr. Bodecker statedin 1878, and also more satisfactorily explains the clinical fact that atthis particular portion of a carious cavity in a tooth, the sensibility ismuch more acute than in other parts of the same tooth. In some instances the crown of the tooth may be nearly coveredwith a well-developed or a stratified and slightly pigmented enamel, CONGENITAL DEFECTS IN ENAMEL. 609 the other portions being coated with a thin layer highly pigmented,again denoting deficiency in lime-salts. (See Fig. 4.) We present here a transverse section of the crown of a thin and irregularly contoured enamel exhibits only transversesections of prisms, of a deep brown color. At the interzonal layernumerous pear-shaped protoplasmic spaces are seen penetrating theenamel, and in the region nearest the dentine the prisms appear as ifgranular or sieve-like (perforated with numerous small holes), indica-tive of a lack of proper calcification. Fig. Imperfect enamel. £, well-developed enamel, transverse section ; G, G, granular layer ofenamel, with pear-shaped protoplasmic enlargements ; D, dentine, canaliculi in transverse andoblique sections ; /, intei globular spaces. I will now call your attention to some extremely interesting andinstructive anomalies in the formation of this tissue, viz : two distinctvarieties of enamel, one upon the other. First we have the anoma-lous portion grafted or deposited upon a normal enamel, and againanomalous enamel first deposited, with the peripheral portion fairlynormal. (See Fig. 5.) This represents a cusp of a molar, with a conspicuously deficientenamel, deposited upon a nearly normal one. The normal portion isslightly pigmented, slightly stratified, and supplied with a moderatenumber of granulations, near the interzonal layer. The outer orperipheral portion exhibits a laVer which ends abruptly on one side, 6io THE DENTAL COSMOS. and gradually blends with the normal enam
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