ULTRASTRUCTURAL OBSERVATIONS OF HOOF HORN FROM DAIRY-COWS - THE STRUCTURE OF THE WHITE LINE

The white line (zona alba) is the specialised region of the bovine cla w capsule at the junction of the wall and the sole. It consists of two distinct components, both generated from epidermis overlying the lami nar corium, and these were examined in the transmission electron micro scope. One constituent of the white line is the laminar horn leaflet w hich was composed of fusiform squames. Within these squames the bundle s of keratin fibres were orientated parallel to the laminar horn leafl ets. The second components, the interdigitating horn, was composed of squames which were polyhedral in outline and contained tightly packed bundles of keratin fibres, orientated in various directions. These dif ferent ultrastructural appearances are thought to be associated with d ifferent mechanical properties for the two parts of the white line. No horn tubules were present in the interdigitating horn of the white li ne.