A text-book of the diseases of the ear for students and practitioners . ) The vertical part, the cells of which communicate with themastoid antrum. The size and shape of the mastoid present many variations. Insome cases, it is massively developed, while in others it is reducedto a short solid protuberance. Wealso find considerable differences inthe internal structure of the mastoidprocess; this, as the older anato-mists already knew, is not alwayscomposed of pneumatic cell-spaces,but is often formed, either com-pletely or partially, of a spongy,fatty, or compact osseous sub-stance (Zoja). Of 2
A text-book of the diseases of the ear for students and practitioners . ) The vertical part, the cells of which communicate with themastoid antrum. The size and shape of the mastoid present many variations. Insome cases, it is massively developed, while in others it is reducedto a short solid protuberance. Wealso find considerable differences inthe internal structure of the mastoidprocess; this, as the older anato-mists already knew, is not alwayscomposed of pneumatic cell-spaces,but is often formed, either com-pletely or partially, of a spongy,fatty, or compact osseous sub-stance (Zoja). Of 250 temporalbones examined by Zuckerkandl,the mastoid process was completelypneumatic in only 368 per cent., partially diploetic and partially pneumatic in 43*2 per cent., andwholly fatty, diploetic, or sclerosed in 20 per cent. We therefore differentiate three principal types : the pneumatic,the diploetic, and the mixed form, a combination of the pneumatic type is often composed of a large number ofirregular cell - spaces, penetrating the temporal bone in all. Fig. 48. 46 DISEASES OF THE EAR directions, and generally covered by a thin, external osseouslamella (Fig. 47). In other cases the whole process consists ofone or two large cavities, or of numerous small cavities inaddition to one or more large ones, which cause the bony cortexat the apex or on its internal surface to stand out like cavities often communicate with the antrum only by anarrow canal. The pneumatic cell-spaces start from the mastoid antrum, extend pos-teriorly to the sutura occipitalis, and surround the sinus transversus andemissariurn Santorini; inferiorly, they reach to the apex and inner surface ofthe mastoid, as well as to the incisura mastoidea; superiorly and anteriorly,they extend to the linea temporalis and the root of the zygomatic process,thereby completely encircling the auditory canal, with the exception of itsanterior inferior wall. They sometimes reach inwards as far as th
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Keywords: ., bookcentury1900, bookdecade1900, booksubjectear, booksubjecteardi
