. The physiology of domestic animals ... Physiology, Comparative; Veterinary physiology. 880 PHYSIOLOGY OF THE DOMESTIC ANIMALS. labyrinth. It connects interiorly with the fauces by the Eustachian tube, and posteriorly with the mastoid cells of the mastoid portion of the tem- poral bone. In some animals these mastoid cells are greatly developed and so form an important augmentation of the tympanic cavit}', while the Eustachian tube, which is short and straight in the case of most rumi- nants, is very much dilated in the horse where it forms what may be termed guttural pouches (Fig. 401). i. II
. The physiology of domestic animals ... Physiology, Comparative; Veterinary physiology. 880 PHYSIOLOGY OF THE DOMESTIC ANIMALS. labyrinth. It connects interiorly with the fauces by the Eustachian tube, and posteriorly with the mastoid cells of the mastoid portion of the tem- poral bone. In some animals these mastoid cells are greatly developed and so form an important augmentation of the tympanic cavit}', while the Eustachian tube, which is short and straight in the case of most rumi- nants, is very much dilated in the horse where it forms what may be termed guttural pouches (Fig. 401). i. Fig. 402.—I. The Mechanics of the Auditory , after Hslm- holtz. II. Section of the Middle Ear, after Hensen. (Mutik.) I. a, malleus; ft, incus: mn. long process of incus ; *, stapes; the arrows show the direction of mo- tion. II. G. external auditory canal; , meuibrana tympani; (', tympanum ; B, malleus ; , superior ligamant; S, stapes. Stretching across the-middle ear from one side to the other is the chain of bones, each named from its resemblance to some instrument; thus, the malleus, so-called from its resemblance to a hammer, is attached to the membravmm of the tympanum by its handle (Fig. 402). The second bone, from its resemblance to an anvil, is called the incus, and is attached on the one side to the malleus and on the other to the stapes or stirrup-bone, which is connected by its base to the membrane of the fenestra ovalis, which opens into the internal ear. All these ossicles are movable on each other, but they have no lateral connection with any structure. Sometimes at the end of the incus is found a separate bone known as the os orbiculare. In the inner boundary of the middle ear is placed, in addition to the oval window, a second, also communicating with the vestibule, and called the fenestra rotunda, or round window. The internal ear, or labyrinth, is composed of bone, and consists of. Please note that these images are extracted from scanned
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