[The so-called "reserve cells" of the human cervical (author's transl)]

I. Basal cells occurring focally beneath the columnar epithelium of the endocervix are generally regarded as "reserve cells". Single "reserve cells" cannot be identified among the columnar epithelial cells. II. Single "reserve cells" would not be needed for the regeneration of the cervical mucosa, since the normal columnar, cells themselves are capable of undergoing mitotic division. During such mitoses the mitotic spindle is located above the regular row of nuclei, the axis of the spindle running parallel to the basement membrane and surface of the cell, so that the daughter cells separate in a horizontal direction. Consequently, the term "reserve cell" with its functional implication is misleading and should be replaced by a more descriptive term such as the "subcylindrical"cell. III. It seems that for development of focal groups of subcylindrical cells according to I the columnar cells must proliferate locally. That proliferation could occur with the axis of the mitotic spindle rotated 90 degrees to be perpendicular to the basement membrane. More likely, however, the columnar cells seem to undergo mitoses with their spindles parallel to the basement membrane and accumulate locally to form two layers. On further proliferation of the basal layer, with the mitotic spindles rotated 90 degrees to be perpendicular to the basement membrane and with desquamation of the overlying columnar cells, the than multilayered epithelium may differentiate by indirect metaplasia into squamous epithelium.