. The comparative anatomy of the domesticated animals. Horses; Veterinary anatomy. 518 BESPIBATORT APPARATUS IN MAMMALIA. Fig. 306. The Nasal Cavities. These cavities are two in number—a right and left—and offer for study : their entrance, or nostrils—the f&ssce, properly called, which constitute these cavities ; and the diverticuli named sinuses. Preparation.—Remove the lower jaw from three heads. On the first of these make two transverse sections, one passing between the second and third molar tooth, the other behind the dental arch. Saw through the second head longitudinally and vertica
. The comparative anatomy of the domesticated animals. Horses; Veterinary anatomy. 518 BESPIBATORT APPARATUS IN MAMMALIA. Fig. 306. The Nasal Cavities. These cavities are two in number—a right and left—and offer for study : their entrance, or nostrils—the f&ssce, properly called, which constitute these cavities ; and the diverticuli named sinuses. Preparation.—Remove the lower jaw from three heads. On the first of these make two transverse sections, one passing between the second and third molar tooth, the other behind the dental arch. Saw through the second head longitudinally and vertically, a little to one side of the median line. On the third make a horizontal section in such a manner as to obtain an inferior portion analogous to that shown in Fig. 41. On this the organ of Jacobson may be studied. 1. The Nostrils. The nostrils (or anterior or inferior nares) are two oblong, lateral openings^ situated at the extremity of the nose, circumscribed by lips or movable tvimjs (aim) disposed in an obhque direction downwards and inwards, and slightly curved on themselves, so as to present their concavity to the external side. The lips or alee of the nostril are enveloped, inwardly and outwardly, by a thin, delicate skin, covered by fine, short haii-s. The exter?ial is concave on its free margin ; the internal is convex. The commissure which unites these two wings superiorly, fonns a slight arch curved inwards. When the finger is introduced into this commissure it does not enter the nasal cavity, but the false nostril—a conical pouch formed by the skin, extending' to the angle comprised between the nasal spine and the ascending process of the premaxillary bone. In the Ass, according to Goubaux, the false nostril is areolated at the posterior extremity, which ascends beyond the summit of the re-entering angle formed by the nasal and premaxillary prolongation. The inferior commissure is round and wide, and, to- wards the bottom, presents an opening, sometimes
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