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Mason, M.J. & Farr, M.R.B. (2013) Flexibility within the middle ears of vertebrates. Journal of Laryngology & Otology 127: 2-14.
In this paper, we consider the middle ear apparatus of amphibians, reptiles, birds and mammals and note that in each case there is some degree of flexibility within the ossicular system. This flexibility is often conveyed by bending of a cartilaginous extracolumella in non-mammalian species, while in mammals it may be the result of relative motion within the interossicular articulations or manubrium. Using a simple model, we demonstrate that flexibility within the ossicular chain is expected to reduce transmission of sound energy, especially at high frequencies. Although there are some theoretical circumstances where it may improve sound transmission, for example as part of a "transmission line", the ubiquity of flexibility within vertebrate middle ears is most obviously linked to the need for protection against changes in static air pressures.
We go on to consider the evidence for flexibility within the human middle ear, the clinical consequences when this flexibility is reduced, and the pros and cons of introducing flexibility into middle ear prostheses.
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