The facility with which instruments can be introduced into the nasal opening of the duct depends upon its position as well as its size. This position varies in different instances. Sometimes it opens directly into the roof of the inferior meatus, in which case the hole is large and round, so that tears readily run into the nose. In other instances the opening is situated on the outer wall of the meatus, and is then always such a narrow fissure as to be hardly discernible. The practical conclusion then is, that a probe can be easily introduced when the opening is in the roof of the meatus, but not without difficulty and laceration of the mucous membrane when on the outer wall. This difficulty indeed may be increased by the narrowness of the meatus, arising from an unusual curvature of the spongy bone. 18. =Nose and nasal cavities.=--The line where the cartilages of the nose are attached to the nasal and superior maxillary bones can be traced with precision. The close connection of the skin to the cartilages admits of no stretching; hence the acute pain felt in erysipelas and boils on the nose. The external aperture of the nose is always placed a little lower than the floor of the nostril, so that the nose must be pulled up before we can inspect its cavities. Looking into the nostrils, we find that the left is, in the majority of cases, narrower than the right, owing to an inclination of the septum towards the left. A communication sometimes exists between them, through a hole in the septum, as in the case of the celebrated anatomist Hildebrandt. By stretching open the anterior nares we can get a view of the end of the inferior spongy bone. The middle spongy bone cannot be seen: its attachment to the ethmoid is high up, nearly opposite the tendo oculi. The cavities are so much narrowed transversely by the spongy bones, that in the extraction of polypi it is better to dilate the blades of the forceps perpendicularly, and near the septum. 19. =Mouth.=--What can be seen and felt through the mouth? The upper surface of the tongue, ‘_speculum primarum viarum_,’ is a study in itself. We notice, on its under surface, a median furrow, on each side of which stands out the ranine vein, lying upon the prominent fibres of the lingualis. In the middle line of the floor of the mouth is the ‘frenum linguæ,’ with the orifice of the duct of the submaxillary gland on each side of it. The gland itself can be detected immediately beneath the mucous membrane by feeling further back near the angle of the jaw, at the same time pressing the gland upwards from below. The long ridge of mucous membrane on each side of the floor contains the sublingual glands. We can feel the attachment of the ‘genio-hyo-glossi’ behind the symphysis of the jaw. The division of this attachment would enable a surgeon to draw the tongue more freely out of the mouth in any attempt to remove carcinoma extending far back into its root.