Principles and practice of operative dentistry . e minute structuresof the embryonic tissues. With the higher powers of the microscope itbecame possible to delve deeper into the mysteries of the evolution of thedental tissues than these old masters had been permitted to do. The re-sults of these investigations have proved conclusively that the enamel-organs had their origin in the epithelial tissues, and hence were formedfrom the same tissue elements as the hair, the nails, and the epitheliallining of the glandular structures of the skin and the mucous membrane,—namely, epithelial cells. EVOLU


Principles and practice of operative dentistry . e minute structuresof the embryonic tissues. With the higher powers of the microscope itbecame possible to delve deeper into the mysteries of the evolution of thedental tissues than these old masters had been permitted to do. The re-sults of these investigations have proved conclusively that the enamel-organs had their origin in the epithelial tissues, and hence were formedfrom the same tissue elements as the hair, the nails, and the epitheliallining of the glandular structures of the skin and the mucous membrane,—namely, epithelial cells. EVOLUTION OF EPITHELIAL TISSUE. In order that the student may approach the subject of the evolution ofthe teeth with a clear understanding of the tissue elements which enterinto their structure, it will be advisable to present in brief review themorphology and the character of epithelial tissue in general. In all animals which are developed from an ovum (Fig. 84), as soon asimpregnation has taken place and the proper conditions of incubation are26. Fig. 84.—Graafian follicles, or ova, in various stares of development. X 80. Fig. 86.—Transverse section of embryo of chick, eighteen hours incubation, showing epiblast andhypoblast. (After Aby.)


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Keywords: ., bookcentury1900, bookdecade1900, booksubjectdentist, bookyear1901