Abstract
The cells of the basal layer of the epidermis send fine cytoplasmic processes to the underlying P.A.S.-positive basement membrane on which the basal cells rest. The delicate collagenous fibres in the papillary layer of the dermis were not distinct from the finer reticular fibres at the dermo-epidermal junction. An extensive network of elastic and reticular fibres was present in the superficial part of the papillary layer and closely approached the basal epidermal cells. It appeared that the framework of the basement membrane was formed by reticular fibres and was also partly supported by fine elastic fibres. The reticular meshwork was in turn filled by a strongly P.A.S.-positive substance which gave the appearance of a homogeneous membrane at the dermo-epidermal interface. The penetration of the cytoplasmic processes into the basement membrane, the enmeshing of the reticular and elastic fibres at the dermo-epidermal junction and the attachment of the reticular fibres to the dermal collagenous fibres, provide the necessary strength for this attachment.