Micrograph of the affected skin. Macroscopically unaffected skin from the left hind leg of a Charolais calf having a subepidermal cleft formation with acellular, proteinaceous fluid (asterisk): the PAS-positive basement membrane (arrow) is located at the floor of the cleft attached to the adjacent dermis. E = epidermis; D = dermis. Periodic acid-Schiff (PAS)-reaction. Bar = 25 μm.