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To the Editor.—Dr. Palva comments that an increased perilymphatic pressure would be more likely to cause compression of the endolymphatic system. This would certainly seem to be true provided the endolymphatic system itself were a normal one. In this case, however, the increased perilymphatic pressure occurred in the presence of an already existing endolymphatic hydrops. Such an increased perilymphatic pressure, therefore, just because of the preexisting increased endolymphatic pressure, might be forced to a different outlet for release and cause erosion and fistulous formation into the surrounding bone.
The tissue filling the sidetracts extending from the aqueduct to the internal auditory canal are definitely filled with arachnoidal tissue, which at times even resembles pacchionian bodies (arachnoidal granulations). This is seen especially in Fig 7 between the two arrows facing each other. There can be no doubt that one of the tracts does open into the internal auditory canal. This