A text-book of the diseases of the ear / by Josef Gruber.

  • Gruber, Josef, 1827-1900.
Date:
1890
Catalogue details

Licence: Public Domain Mark

Credit: A text-book of the diseases of the ear / by Josef Gruber. Source: Wellcome Collection.

    82/618 (page 48)
    shorter than those of sudoriferous glands, have a diameter of 005 — o 06 mm. ; whereas the gland measures 0-2—0'8 mm. According to most observers, the gland duct consists of a homogeneous membrane surrounded externally by a layer of longitudinal smooth muscular fibres, beyond which is a layer of connective tissue. The lumen of the duct is lined with cells (Kölliker). These glands secrete the cerumen, which in the fresh condition is of a bright yellow colour, and nearly fluid. On exposure to the air it becomes firm and darker in colour, and may form brown plugs or crusts. The muscular bands which are described as the muscles of the auditory canal, are situated on the anterior wall of its cartilaginous portion, and consist of: (1) The m. incisures Santorini, which passes over the fissures on the anterior surface of the cartilage ; (2) Thestylo-auricularis—described by Hyrtl, and said to be present in about one out of every six cases—which arises from the upper part of the styloid process, and is inserted by a fan-shaped tendon close to the inner part of the cartilage of the canal. (c) The Tympanic Membrane, tympani, s. diaphragm, s. myrinx, s. Fig. 32. Outer surface of the tympanic membrane, (1^ times the natural size). G, Handle of malleus; kf, short process (cartilaginous structure) ; ue, lower end of handle of malleus; hf, posterior fold. ■The tympanic membrane {jnembrana upturn membranacatm, s. operimentum Fig. 33- Inner surface of the tympanic membrane, with malleus and incus. E! li s K, Head of malleus; K', body of incus ; hs, horizontal (short) process of incus ; ps, perpendicular (long) process of incus; cht, cht', chorda tympani; tt, place of in- sertion of tensor tympani ; G, handle of malleus; tic, lowerend of handle of malleus. auris) (Figs. 32, 33) is stretched across the inner end of the auditory canal, forming the partition wall between it and the tympanic cavity. The membrane, like the opening which it fills up, has the form of a somewhat bent ellipsoid, its greatest diameter (vertical) being from 9-10 mm., while its transverse diameter is from 8-9 mm. So far as the inner end of the auditory canal is formed by the tympanic portion (tympanic ring), the membrane is fixed in a groove (sulcus tympanicus); but there is no proper groove for its insertion into that portion which is formed by the horizontal part of the squama. In the child, the membrana tympani lies more horizontal than it does