study of that of some lower vertebrate. We shall describe its main
features now, but their meaning will be much clearer after the lower
type is read. Our figures are of Canis. In section (Figure VI., Sheet 6),
we perceive a brain case (cranium) opening behind by a large
aperture, the foramen magnum (F.M.). In front of this is an extensive
passage, the nasal passage (E.N. to P.N.) which is divided from the
mouth by a bony floor, the palate, and which opens into the pharynx
behind at the posterior nares (P.N.) and to the exterior by the anterior
or external nares (E.N.). It is divided into right and left passages by a
middle partition, the nasal septum. Outside the skull, on its wings, is
a flask-like bone, the bulla tympani (b. in Figures 2 and 3), protecting
the middle ear, and from above this there passes an arch, the cheek
bone (ju. in Figures 1, 2, and 3), to the upper jaw, forming in front the
bony lower protection of the cavity containing the eye, the orbit. The
cheek arch, nasal passage, and jaws, form collectively the "facial
apparatus," as distinguished from the cranium, and the whole skull is
sometimes referred to as, the "cranio-facial apparatus." Two
eminences for articulation with the atlas vertebra, the condyles (c.), lie
one on each side of the lower boundary of the foramen magnum.