. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. P honor eception 489 Reptiles. It is in certain reptiles that structures characteristic of a true coch- lea make their first appearance (Figs. 161, 166). In alligators the lagena is attached to two sides of the surrounding cavity, therehy forming three ductsâ the scalae vestihuli, media, and tympani,âand the floor of the lagena forms the basilar membrane. In all reptiles other than snakes there is a middle ear which contains a bony structure similar to the columella of frogs, except that it usually is composed o


. Comparative animal physiology. Physiology, Comparative; Physiology, Comparative. P honor eception 489 Reptiles. It is in certain reptiles that structures characteristic of a true coch- lea make their first appearance (Figs. 161, 166). In alligators the lagena is attached to two sides of the surrounding cavity, therehy forming three ductsâ the scalae vestihuli, media, and tympani,âand the floor of the lagena forms the basilar membrane. In all reptiles other than snakes there is a middle ear which contains a bony structure similar to the columella of frogs, except that it usually is composed of two bones. The tympanic membrane is usually de- pressed below the body surface to form an external auditory meatus, and in alligators there is even a skin fold which may serve as an outer ear. Snakes have no middle ear, and the outer end of the columella is attached to the quadrate bone of the skull. This arrangement makes snakes (even the cobra!) insensitive to air-borne sounds but very sensitive to earth-borne vibra- tions, such as those resulting from the footfalls of approaching animals. There is considerable evidence that rattlesnakes cannot hear their own ratthng.^"'' 4ndolymph duct brain. anterior canal posterior canal lateral canal extra â columella tympanic membrane Fig. lagena stapes 166. Diagrammatic presentation of the ear of a reptile, as seen from the posterior. (Adams.') The microphonic effect and the auditory nerve responses of reptiles have been studied by several investigators. Foa and Peroni^-' recorded impulses from the auditory nerve of Thalassochelys. Wever and Bray"'-^ found a microphonic effect between 120 and 1000 cycles for Chrysemys picta, with a high response below 500, and Adrian- found that the ear of Cistudo responded only to the narrow band of 80 to 130 cycles, with a maxi- mum at 110 cycles, and the impulse frequency of the nerve was the same as the stimulating frequency. A snake gave an irregular nerve response dis- charge in res


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