The =nostrils= are small, and are situated on the flat anterior surface
of the =rostrum= or snout (Rostrum suis). The latter is a short
cylindrical projection, with which the upper lip is fused, and is
circumscribed by a prominent circular margin. The skin on the snout is
thin and highly sensitive; it presents small pores, and scattered over
it are fine short hairs. In the snout between the nostrils is the =os
rostri=, which is to be regarded as a special development of the
extremity of the septum nasi in adaptation to the habit of rooting. A
plate of cartilage, representing the lamina of the alar cartilage of the
horse, curves outward and downward from the upper part of the os rostri
and a pointed bar of cartilage curves upward from the lower part of the
bone in the outer wing of the nostril. The notch between the nasal bone
and the premaxilla is closed in by parietal cartilages which resemble
those of the ox.
The =nasal cavity= is long and narrow. It is divided behind by a
horizontal plate into an upper olfactory part, which leads to the
ethmoidal meatuses, and a lower respiratory part, which is a direct
continuation of the inferior meatus. The posterior part of the septum is
membranous.
The =turbinal bones= resemble in general those of the ox. The =superior
meatus= is exceedingly small. The =middle meatus= is a deep fissure
between the two turbinals: it divides posteriorly into two branches; one
of these extends upward and backward between the lateral mass of the
ethmoid bone and the superior turbinal; the other widens and joins the
inferior meatus. The opening between the maxillary sinus and the middle
meatus lies in a plane through the last cheek teeth. The middle meatus
is continuous with the space inclosed by the dorsal part of the inferior
turbinal and with the cavity of the superior turbinal. The dorsal
division of the middle meatus presents several openings into the frontal
sinus. The =inferior meatus= is relatively roomy; it communicates with
the space inclosed by the ventral coil of the inferior turbinal. The
opening of the naso-lacrimal duct is found in the posterior part of the
inferior meatus. The naso-palatine duct and the vomero-nasal organ (of
Jacobson) resemble those of the ox.