Direction of Flow of Nasal Mucus

Information concerning patterns of ciliary movement in the nose of man and monkey is already available, but in order to learn the significance of the direction of mucous flow in various regions of the nose and its possible relation to physiological and anatomical factors, experiments were performed on numerous mammals, selected to include a wide range in size, the mouse, rat, rabbit, opossum, cat, sheep and cow. The animals were decapitated and the lateral nasal wall exposed by cutting near the median line. Two methods were employed which doubly insured accuracy; one, the application of carbon particles to the mucous surface, is well known; and the second, which leaves the mucous layer undisturbed and permits the moving cilia themselves to be observed in situ, has recently been described. It was found, as a result of these experiments, that the mucous flow in the upper half to two-thirds of the lateral nasal wall including the middle meatus, is toward the anterior end of the nose in all the animals mentioned. Only the material collected from the ethmoid conchae and those regions adjacent to the floor arrives in the nasopharynx. The material derived from the ostium of the maxillary sinus spreads, fan-like, to be distributed toward the anterior end, the floor, and the nasopharynx. Evidently the direction of ciliary beat is adapted to protect the non-vibratile olfactory epithelium from accumulation of mucus along its border. This should be taken into account when fluids, bacterial suspensions, and viruses are experimentally introduced into the nose with the expectation that they will pass through the cribriform plate as a portal of entry into the central nervous system. The entire mucous sheet in man and monkey ultimately reaches the nasopharynx and none passes out of the anterior nares, which is quite different from the condition found in the animals described and in the latter the region of greatest ciliary activity is in the upper part of the nose and the flow of mucus in the lower half and along the floor is very sluggish. This also is exactly opposite to the condition found in man and monkey.