A Small Granular Component of the Cytoplasm of Keratinizing Epithelia

We have often observed small dense bodies in the cytoplasm of cells of the stratum granulosum during a study of the fine structure of normal and experimentally altered mouse ear epidermis. Odland (10) noted their presence in human epidermis, showed that they have an internal structure, and speculated that they may be degenerating mitochondria. Other authors seem to have overlooked them in their descriptions of the fine structure of skin, although the bodies appear in their micrographs (1, 6, 9, 11, 12). These small bodies appear to be a normal component of the cytoplasm of keratinizing epithelia, and may play some role in keratinization. We suggest that these bodies be referred to as corpuscula. MATERIALS AND METHODS Electron microscopic observations were made on the ear epidermis of eight normal adult male Swiss albino mice, and four adult male Swiss albino mice whose skin was made hyperplastic by topical applications of 5 per cent croton oil in liquid paraffin twice a week for 5 weeks. Specimens of ear epidermis were removed while the mice were under ether anesthesia. The specimens were fixed in either cold buffered 1 per cent isotonic osmium tetroxide (16) or cold buffered 2 per cent isotonic potassium permanganate (4) for periods ranging from 10 to 60 minutes, and were dehydrated and embedded in Epon by LufFs method (5). Sections were cut on either an LKB or a Porter-Blum microtome with a glass knife, mounted on carbonized Formvar-coated grids, stained with lead hydroxide for 15 minutes (14), and examined in an RCA EMU 3E microscope. OBSERVATIONS Despite minor modifications in techniques of fixation and embedding, the fine structure of the epidermis as seen in our preparations of the mouse