Volume 1

System of diseases of the ear, nose, and throat / edited by Charles H. Burnett.

  • Burnett, Charles H. (Charles Henry), 1842-1902.
Date:
1893
Catalogue details

Licence: Public Domain Mark

Credit: System of diseases of the ear, nose, and throat / edited by Charles H. Burnett. Source: Wellcome Collection.

Provider: This material has been provided by University of Bristol Library. The original may be consulted at University of Bristol Library.

    34/842 (page 12)
    between the internal meatus and the aquseductus vestibuli, there is a small foramen or fissure, which is the remnant of the large fossa subarcuata of the foetus. The anterior or upper surface (Fig. 2) of the pyramid looks upward, forward, and outward, and forms part of the middle fossa of the base of the skull. A depression near its apex lodges the Gasserian ganglion. From the free edge of its anterior border a narrow groove runs longitudinally outward and backward to a foramen at about the centre of this surface, called the hiatus Fallopii, which leads to the aqueduct of Fallopius and transmits the great superficial petrosal nerve. Parallel to this groove, and on its outer side, close to the canal for the tensor tympani muscle, there are a smaller groove and a foramen for the lesser superficial petrosal nerve. Outward and backward from these foramina there is a rounded eminence indicating the position of the superior semicircular canal. The angle formed by the superior surface of the petrous portion and the inner surface of the squamous portion is grooved for the reception of the petro-squamosal sinus, and also shows traces of the petro-squamosal fissure. This fissure begins at the re-entering angle between these two portions, and can be traced less and less distinctly to the posterior border of the bone. The bone lying between this fissure, the eminence of the superior semicircular canal, and the hiatus Fallopii and groove, is a thin lamella, sometimes perforated, which rests on the mastoid antrum, the tym¬ panum, and the canal is musculo-tubarius. The part over the mastoid antrum is called the tegmen mastoideum ; that over the tympanum, the tegvnen tym¬ pani. The tegmen mastoideo-tympanicum slopes forward, outward, and downward,—forward about forty-five degrees, outward about forty-five degrees, and downward from five to twenty degrees, the majority slanting about ten degrees; therefore the tegmen mastoideum is but a little higher than the tegmen tympani. These measurements of level are referred to the upper border of the zygoma and its posterior root as a horizontal line. The following: measurements of the minimum vertical distance from the upper wall of the osseous meatus to the inner surface of the tegmen tympani were taken on fifty-five macerated adult bones. The bones were levelled by placing the upper border of the zygoma and the horizontal part of the linea temporalis in a horizontal position. The place on the wall of the meatus which approached nearest the cranial cavity had no fixed position, varying between zero and six millimetres from the external orifice of the meatus, and averaging three and one-third millimetres. The thickest was nine and a half millimetres; the thinnest was two millimetres; the average was four and sixty-nine-hundredths millimetres. There were twenty measure¬ ments between four and five millimetres. The superior border of the petrous bone is directed inward and forward, and slants downward. It is grooved for the superior petrosal sinus. From the inner end of this border there is often a little projecting spine over¬ lapping the inferior petrosal sinus, which gives attachment to the petro-