The development of the human body : a manual of human embryology / by J. Playfair McMurrich.

  • McMurrich J. Playfair (James Playfair), 1859-1939.
Date:
1910
Catalogue details

Licence: In copyright

Credit: The development of the human body : a manual of human embryology / by J. Playfair McMurrich. Source: Wellcome Collection.

Provider: This material has been provided by the Royal College of Physicians of Edinburgh. The original may be consulted at the Royal College of Physicians of Edinburgh.

    487/546 (page 473)
    it passes intothejubsta^^ on the way to its destination. The m£!£i^ ^ ^^'^^^ ^^'^'^ structures are Embedded is rather voluminous (Fig. 257), and after the end of the seventh month becomes converted into a peculiar spongy tissue, ^ .......^..-..y.^^^^.^y^..^^ which, toward the end of fetal life, gradually degenerates, the - •. tympanic cavity at the same ^ ] time expanding and wrapping ^ itself around the ossicles and the muscles attached to them V .^^ (Fig. 256). The bones and / (jjjj^^ \ j their muscles, consequently, m ; j^^ while appearing in the ;idult to \ ^ traverse the tympanic cavity, - ^ are really completely enclosed within a layer of epithelium ^ ,.- continuous with that lining the viPl''^ wall of the cavity, while the \ handle of the malleus and the ' \ ^ chorda tympani lie between the ■••.!b»w««ssk»«» epithelium of the outer wail Fig. 256.—Diagrams Illus- L .■■.■„, . - . - TRATING THE MODE OF Kx- of the cavity and the fibrous tension of the Tympanic lgg£cjerm_wl.ich forms tlie CA^Si-^ ™' tympanic membrane. U, Malleus; w, spongy mesen- The extension of the tvm- f^y'^^:. f.- inner surface of the penotic capsule; T, tym- panic cavity does not, however, panic cavity. The broken • ,i -i. 1 4. r line represents the epithelial cease witn its replacement or lining of the tympanic cavity. the degenerated spongy mesen- chyme, but toward the end of fetal life it begins to invade the substance of the temporal bone by a process similar to that which produces the ethmoidal cells and the other osse- ous sinuses in connection with the nasal cavities (see p. 186). This process continues for some years after birth 41