Cartilage in the bony portion of the eustachian tube.

The distribution of cartilage in the bony section of the eustachian tube was studied by examining histological serial sections of 50 temporal bones of infants and adults. When cartilage was found to be present in the bony segments of the eustachian tube, its cross-sectional area was measured. Cartilage was seen in the isthmic region in all specimens. In the post-isthmic region it was present in all of the specimens taken from infants and in 92.3% of the adult specimens. In the pretympanic region cartilage was found in 34.6% of the infants' eustachian tubes and in 25% of the adults'. The results indicate that cartilage is also present in the bony part of the eustachian tube at all ages but diminishes in frequency the more the eustachian tube approaches the middle ear.