Fig. 1. Diagrammatic transverse section of the left middle ear of a female bullfrog, seen from the caudal direction: lateral is towards the left. Cartilage is stippled. The pars media and pars interna are collectively referred to as the stapes. The hinge-like articulation between the pars media and the otic capsule, along the ventral rim of the oval window, forms the `footplate axis'. Reflective beads, representing points from which laser measurements were made, are represented by small circles on the tympanic membrane, extrastapes and stapes footplate. The tympanic membrane of a male frog would be greater in diameter and would have a large, fatty pad at its centre.

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