The diseases of the ear and their treatment . changes are caused in the tympanum by removal of the glosso-pharyngeal or by extirpation of the superior cervical ganglion. Posteriorly and externally the tympanic cavity is connectedwith the air-cells of the mastoid process, which, before they passinto the tympanum, form a common cavity, the antrum lies at the posterior and upper part of the inner half of the DISEASES OF THE MIDDLE EAR. 125 osseous meatus, and is separated from it by an osseous layer 3—4mm. thick. The air-cells extend over the whole mastoid process,and are
The diseases of the ear and their treatment . changes are caused in the tympanum by removal of the glosso-pharyngeal or by extirpation of the superior cervical ganglion. Posteriorly and externally the tympanic cavity is connectedwith the air-cells of the mastoid process, which, before they passinto the tympanum, form a common cavity, the antrum lies at the posterior and upper part of the inner half of the DISEASES OF THE MIDDLE EAR. 125 osseous meatus, and is separated from it by an osseous layer 3—4mm. thick. The air-cells extend over the whole mastoid process,and are also frequently met with between the superior wall of themeatus and the middle cranial fossa. Their total extent chieflydepends upon the conformation of the lateral sinus running intothe sigmoid fossa, and also that of the middle fossa of the to the authors measurements,1 which agree with thoseof Bezold, the distance between the sigmoid fossa and the pos-terior wall of the meatus is frequently only a few millimetres. The. Fig. 30. Fig. 31. M. Meatus auditorius externus. F. Fossa sigmoidea. variations which are met with in this respect are very considerable,as is seen in Figs. 28 and 29, which represent sections made per- 1 Von Langenbecks Archiv für Chirurgie, vol. xxi. 126 DISEASES OE THE MIDDLE EAR. pendicularly to the axis of the meatus, and in Figs. 30 and 31,which are sections made horizontally through the middle line ofthe meatus, the one showing a shallow and the other a deep exca-vation of the sinus. When this excavation is great, and the middlecranial fossa is only separated from the superior wall of the meatusby a thin layer of bone (a condition which the author has describedas a low-lying middle cranial fossa, Fig. 29), the space occupiedby cell-cavities is greatly reduced. When the lateral sinus advancesstrongly forward, it at the same time assumes an outward direction(Fig. 31), so that, in extreme instances, like the two represented,the mastoid
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