Abstract
1) The lumen of the sudoriferous duct, all along its passage from the surface of the skin to the deepest level of the stratum corneum, is lined by concentrically and epithelially arranged flattened cells, the layers of which are presumably three in number (fig. 1).
2) An additional proof for the fact that the duct in the stratum corneum is a tubular structure with a wall of its own is afforded by an experiment, in which a fairly thick slice taken from the surface of the skin is heated in a solution of caustic potash. The cells constituting the wall of the duct are more resistant than the general cells of the stratum corneum, so that a tubular form remains (fig. 2).
3) In the stratum germinativum, nucleated and epithelially arranged cells, presumably in three layers, surround the lumen of the sudoriferous duct, some of them containing keratohyalin granules in the cytoplasm (fig. 3).
4) The sudoriferous duct in the corium has an epithelium consisting definitely of three layers of cells. The innermost layer is made up of cuboidal cells, while the outer two layers are constituted by more flattened cells. All the cell layers are continued, without any observable change in arrangement and character of cells, to those of the sudoriferous duct in the stratum germinativum. Hence, it is assumed that the cell layers of the duct in the stratum germinativum and at the upper levels of the epidermis are also three in number, although this is obscured by the circumstances that the neighboring epidermal cells are flattened by pressure and so deformed to appear as if they form more layers of cells over the proper wall of the duct (fig. 4).
5) The duct in the epidermis is thought to be continually regenerated by multiplication of its cells presumably at the deeper levels of the stratum germinativum. The duct cells, as they reach the upper levels of the epidermis, undergo keratinization, which is more precocious than in the epidermal cells at the same level. Moreover, the innermost layer of them precedes the outer two layers in that process.
