The middle ear of a lion: comparison of structure and function to domestic cat.

Acoustic and anatomical measurements were made on the middle ear of a deceased lion and compared with measurements from the domestic cat. The acoustic input impedance and sound-transmission ratios measured in the two species have similar features but differ quantitatively. Three-dimensional anatomical reconstructions show that the middle-ear structures of the lion and cat are similarly arranged but have large differences in absolute and relative size. In all fields, a bony septum divides the middle-ear air space into two cavities that are coupled through a small opening. A six-element analog-circuit model based on this distinctive structure captures the main features of both sets of middle-ear frequency responses, except at high frequencies. The element values are consistent with the structural dimensions of the cavities. The results suggest that quantitative measures of middle-ear cavity structure could allow prediction of frequency-dependent features of acoustic sensitivity for the entire cat family.