A manual of otology for students and practitioners . s composed mainly of diploetictissue which is separated more or less completely fromthe antrum bv a denser lamina of bone. There is even > Fig. 52.—Pneumatic mastoid, cortex removed. External view. at this early stage a great variation in the amount ofdiploetic tissue, and therefore of the position of the a mastoiditis in an infant this tissue may be com-pletely broken down, laying bare the sinus plate or eventhe sinus, or it may have resisted invasion. It is in thisdiploetic tissue that the cells of the mastoid are formedand eve
A manual of otology for students and practitioners . s composed mainly of diploetictissue which is separated more or less completely fromthe antrum bv a denser lamina of bone. There is even > Fig. 52.—Pneumatic mastoid, cortex removed. External view. at this early stage a great variation in the amount ofdiploetic tissue, and therefore of the position of the a mastoiditis in an infant this tissue may be com-pletely broken down, laying bare the sinus plate or eventhe sinus, or it may have resisted invasion. It is in thisdiploetic tissue that the cells of the mastoid are formedand even at this early stage of development of the boneits future type may be foreshadowed. x\ccording to thisvariation of the contents of the mastoid process, the bones ANATOMY 191 are usually divided into pneumatic, diploetic and sclerotictypes. These types can be recognized more or less plainlyat operation or upon examining dry specimens and havewithout doubt a great influence in deciding the formwhich an inflammatory process in the mastoid may Fig. 53.—Pneumatic mastoid. Superior view of ^temporal bone.(Mr. Burchells dissection.) The inner table removed showing the cellsextending well into the petrous tip. Pneumatic Type. — In the fully developed pneumatictype of bone, the mastoid cavity is completely occupiedby cells, the septa between which are thin and shell-like(Figs. 52, 53, and 54). They extend into the tip, fre-quently back over the sinus, at times even into the occipi-tal bone; into the angle formed by the middle fossa andthe recession of the sinus plate above the knee, forward 192 MASTOIDITIS into the posterior root of the zygoma and upward intothe squama. This is a distinctly pneumatic type. Onthe other hand, one sees bones with a thick ivory-Ukecortex and a few cells with thick sclerotic walls, reallya sclerotic mastoid containing a few cells. Betweenthese two extremes may be found any grade in the degreeof the cellular development of the bone. When but afe
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Keywords: ., boo, bookcentury1900, bookdecade1910, booksubjectear, bookyear1916
