Intermediate epithelium.

In the nasopharynx, the larynx, the anal canal and the auditory tube, the "intermediate epithelium" occupied the transitional zone between the ciliated (or nonciliated) columnar epithelium and the stratified squamous one. The intermediate epithelium showed gradations ranging from stratified low-columnar through stratified cuboidal to stratified squamous type. It was suggested that the intermediate epithelium showed the various stages of the epithelium transforming from the columnar to the squamous epithelium, and that the basal cells of the columnar epithelium served as the germinal layer of the transformation.