The tongue of the house-mouse is covered with a completely keratinized epithelium, and the horny cells present show clear morphological and chemical differences in the various sites. Filiform papillae are the only tongue papillae present in the mouse, and these are grouped closely together over the dorsum of the tongue, being responsible for its rough feel. The filiform papilla appears to be a discrete epithelial appendage and is more complex in structure than that of the human tongue. In the mid-dorsal region a central keratinized spine rich in disulphide bonds arise from the base of each papilla. A granular layer is confined to the anterior side of each papilla and there are clear differences in the keratinized cells of the anterior and posterior limbs. Between the papillae, the dorsal epithelium also contains a granular layer, over which a characteristic type of horny layer is formed, without basophilic nuclear remnants. The ventral epithelium mostly contains basophilic nuclear remnants and lacks a granular layer, but granular cells and a horny layer without nuclei occur in localized areas. Differences in the reactions for protein-bound cystine, cysteine, phospholipid, and calcium were demonstrated and are related to the complex histological structure of the keratinized epithelium. © 1969.
