The Dental cosmos . onot reach the surface of the enamel, but at a given distance from itthey are replaced by irregular angular pieces. The outermost por-tion of the lump is of a dark brown color. Penetrating the enamelat varying heights are seen numerous pear-shaped prolongations ofthe dentinal canaliculi, some extending nearly to the surface. Thesespaces contain protoplasm, and have become stained a deep violetcolor by the chloride of gold. Aside from these irregularities thelump seems to be thoroughly calcified, except in a few spots upon thesurface, which have taken a slight violet stain.
The Dental cosmos . onot reach the surface of the enamel, but at a given distance from itthey are replaced by irregular angular pieces. The outermost por-tion of the lump is of a dark brown color. Penetrating the enamelat varying heights are seen numerous pear-shaped prolongations ofthe dentinal canaliculi, some extending nearly to the surface. Thesespaces contain protoplasm, and have become stained a deep violetcolor by the chloride of gold. Aside from these irregularities thelump seems to be thoroughly calcified, except in a few spots upon thesurface, which have taken a slight violet stain. The exposed dentine 6o8 THE DENTAL COSMOS. is also deeply stained the characteristic violet color in this locality,denoting insufficiency of lime-salts, or an excess, over the ordinary,•of organic material. I wish at this point to call attention to a paper just prepared by I. Hart, of New York, in which he has shown beyond a possibledoubt, by means of protracted staining with chloride of gold, that Fig. Isolated lump of enamel, very imperfect. P, P, P, protoplasmic projections into the enamelfrom the dentine; C, transverse section of enamel-prisms. X 500. immediately beneath the enamel, in the dentine, there is a very minutereticulum of living matter, considerably more than is found in otherportions 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 transversesect
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