Textbook of normal histology: including an account of the development of the tissues and of the organs . issue, while in the adult the intercellular fibrous tissue so overwhelmsthe cellular elements that reagents are frequently necessary to satis-factorily demonstrate their existence. While increase of the intercellular substance usually accompaniesthe growth of the mesodermic tissues, those derived from theecto- and entoderm present a marked contrast. In these lattertissues the intercellular constituent is represented by the very scantycement substance, increase in which occurs only as necess
Textbook of normal histology: including an account of the development of the tissues and of the organs . issue, while in the adult the intercellular fibrous tissue so overwhelmsthe cellular elements that reagents are frequently necessary to satis-factorily demonstrate their existence. While increase of the intercellular substance usually accompaniesthe growth of the mesodermic tissues, those derived from theecto- and entoderm present a marked contrast. In these lattertissues the intercellular constituent is represented by the very scantycement substance, increase in which occurs only as necessitated bythe growth of the surrounding cells, the proportion between the twoelements being practically constant throughout life. Instances ofthis constant relation are seen in the varieties and modifications ofthe epithelial tissues. The primary blastodermic layers—ectoderm, mesoderm, andentoderm—early exhibit histological differences which suffice todistinguish the one from the other, and especially to indicate, at leastin a general manner, the tendency of the outer and inner layers to Fig. Blastodermic layers of rabbit embryo: a, ectoderm ; b, entoderm ; c, entodermal cells destined toform notochord ; m, mesoderm. form epithelial structures in contrast to the less compact and morereticular formations of the mesoderm. The epithelia of the genito-urinary tract, however, are marked exceptions in their origin, beingderived, as well as the connective and muscular tissues, from themesoderm, in this respect constituting conspicuous specializations. THE CELL AND THE TISSUES. 2$ Derivatives of the Primary Blastodermic Layers. From the ectoderm are derived— The epithelium of the outer surface of the body, including thatof the conjunctiva and anterior surface of the cornea, theexternal auditory canal, together with the epithelial append-ages of the skin, as hair, nails, sebaceous and sweat glands(including the involuntary muscle of the latter). The epithelium of the nasal tra
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Keywords: ., bookauthorpiersolgeorgeageorgea, bookcentury1800, bookdecade1890
