SUMMARY.— Electron microscope studies have been made on 2 patients suffering from Darier's disease. The changes observed in the desmosometonofilament complex in the acantholytic process differ from those previously reported. The structure and formation of “corps rond’ are described; similar changes also occur in groups of cells apparently involved together.

The ultrastructural changes in extragenital lichen sclerosus et atrophicus have been studied in four cases. The most pronounced changes arc present in the dermis, where there are collagen degeneration and regeneration and increased amounts of elastin. The basal lamina shows holes, long gaps, and replication. Degenerate dermal material passes into the epidermis, which has increased numbers of Langerhans' cells and decreased numbers of melanocytes. These phenomena are discussed.

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SUMMARY The ultrastructural features of two cases of porokeratosis of Mibelli are described. They demonstrate that the basophilic granular material in the cornoid lamella consists of whole degenerate cells with pyknotic nuclei. The dermis contains clumps of a finely fibrillar material and some collagen, and many fibroblasts show degenerative changes.

Guinea-pig epidermal cells were grown on 2 types of rat collagen substrate. The cells showed the same sort of differentiation as occurs in cells growing on rigid plastic. In addition, basal lamina formed patchily at the interface with collagen. If the collagen was eroded away the basal lamina also disappeared.