Three-dimensional structures of the equine hoof were examined by means of a scanning electron microscope. Prior to the examination, small blocks of materials taken from various parts of the hoof were separated in epidermis and corium layer respectively, by maceration with 1% acetic acid or saturated barium hydroxide solution. The findings obtained were compared to the usual histological pictures. The following results were obtained.
1. The appearance of the papillae and laminae of the corium showed clearly under the scanning electron microscopy. The structure of the papillae was in principle the same over the entire corium of the hoof, but the coronary papillae were longer than those of the sole and the frog. The cellular elements surrounding the papillae became flat-formed and resulted in a fibrilar-form by the process of cornification.
2. The epidermal laminae and horn tubes of the epidermis also revealed clearly. The epidermal laminae of the wall run in parallel raws on the inside of the wall from the coronal groove to the ventral edge. They formed the secondary epidermal laminae. These epidermal laminae were interdigitated tightly with the corresponding epidermal laminae.
3. The corona, sole and frog epidermis had numerous horn tubes with the corresponding papillae. The entrance of the horn tubes showed as a funnel-shaped opening. The intertubular horns were a highly keratinized dense tissue. The thin layers of incompletely keratinized tissue run in layers in this horny matrix.
4. The epidermis of the frog was different from the one of the wall and the frog. It was composed of incompletely keratinized horn tubes and intertubular horns, which composed a network of elastic fibers. The junction of the wall and the sole at the white line was tightly connected by gross fibrous elements.