. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. 1, from goat; S, herriiig; rp; 8, nj; », iWk; »,. , In Kgioii of Wnd-bralji, to i, hind-limin: N, •ndlwrjr of cocUm: a. r, tecewM m of •iidit«»7 nenre. HEARINO. 571 perilymph. There is a fenestra oralis, but not a fenestra ro- tunda, though the latter is present in reptiles. In crocodiles and birds the cochlea is tubular, straight, and divided into a Boala tympani and a scal
. A text-book of comparative physiology [microform] : for students and practitioners of comparative (veterinary) medicine. Physiology, Comparative; Veterinary physiology; Physiologie comparée; Physiologie vétérinaire. 1, from goat; S, herriiig; rp; 8, nj; », iWk; »,. , In Kgioii of Wnd-bralji, to i, hind-limin: N, •ndlwrjr of cocUm: a. r, tecewM m of •iidit«»7 nenre. HEARINO. 571 perilymph. There is a fenestra oralis, but not a fenestra ro- tunda, though the latter is present in reptiles. In crocodiles and birds the cochlea is tubular, straight, and divided into a Boala tympani and a scala vestibuli. The columella of lowe.' forms still persists. In birds and mammals the bone back of the ear is hollowed out to some extent and communicates with the tympanum. Bxcept among the very lowest mammals (Echidna), the ear is such as has been described in detail already. Xvolation.—The above brief description of the auditory organ in different groups of the animal kingdom will suiflce to show that there has been a progressive development or increasing differentiation of structure, while the facts of physiology point to a corresponding progress in function—in other words, there has been an evolution. No doubt natural selection has played a great part It has been suggested that this is illustrated by cats, that can hear the high tones produced by mice, which would be inaudible to most mammals ; and, as the very exist- ence of such animals must depend on their detecting their prey, it is possible to understand how this principle has iterated to detennine even what cats shall survive. The author has noticed that terrier dogs also have a very acute sense of hearing, and they also kill rats, etc. But, unless it be denied that the im- provement from use and the reveite can be inherited, this factor must also be taken into the account There seem to be great differences between hearing as it exists in man and in lower forms. Birds, a&d at least some horses, possi
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