[Surface of the olfactory region in man observed by scanning electron microscope].

This report describes the surface of the regio olfactoria of a 25-year-old man as observed in the scanning electron-microscope. Corresponding to the distal ends of the receptor cells, the surface displays various planes: (a) Upper-most is a film of mucus of varying thickness. (b) The olfactory hairs, which are arranged closely together, mostly in a parallel fashion in layers, dip into this mucus film. The long, distal parts of the olfactory hairs are of a rather uniform shape and form, together with the mucus film, a single functional unit. (c) Now follows a layer consisting of the short parts of the olfactory hairs. They branch from the olfactory vesiculae, mostly in a stellar fashion (5-12 on one vesicula) and arch themselves, after a short course, into the mucus film. (d) There then follows the plane of the olfactory vesiculae, mostly bulbous, partly club- and pyramidal in shape. (e) After that comes the plane of the microvilli receptors, which have about 100 or more villi on one cell. (f) Right at the bottom is the apical surface of the supporting cells, different in size, showing microvilli in a regularly arranged pattern. Because of the various planes of the surface of the olfactory region and because of the close situation of the long, distal parts of the olfactory hairs and their rather uniform shape, one could assume, from observations in the scanning electron microscope, that the olfactory-active molecules react immediately with the functional unit of mucus film and long distal parts of the olfactory hairs, so that for the different sense of smell, a quite different structure of the olfactory-active molecules must be assumed as a different shape of the distal ends of the olfactory receptors.