Page:Laboratory Manual of the Anatomy of the Rat (Hunt 1924).djvu/36

22 maxillary bone. The process is attached to the vomer along the median suture of the hard palate. The vomer forms part of the nasal septum. The elongated maxilloturbinal bone attaches to the inner surface of the premaxillary. It lies lengthwise of the nasal cavity and extends upward from its line of attachment.

The zygomatic bone is a small bow-shaped element of membranous origin, joining the zygomatic processes of the maxillary and squamosal bones, thus completing the zygomatic arch.

This fragile bone, which is membranous in origin, comprises the ventral portion of the nasal septum. It unites ventrally with the premaxillary bone. It splits dorsally into two longitudinal lamina, between which the cartilaginous part of the nasal septum is inserted. The posterior part of the bone is without a ventral attachment.

The nasal bones roof the anterior nares and the nasal cavity back to the frontal bones. The ventral surface is concave, both the lateral and the median borders bearing a flange. The median flanges of the two nasals unite to form a ridge for the attachment of the nasal septum. The lateral flange articulates with the frontal process of the premaxillary bone. This flange is widest where the nasoturbinal bone (see longitudinal section of the skull) is attached to it. The line of attachment of the nasoturbinal runs forward and medially from this point. The nasal bone is a membrane bone.