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A newly developed method processing native horn for ultra-thin-sectioning was used to study the structure of perioplic horn by transmission electron microscopy. This modified technique allows the processing of unfixed material and is therefore very economical because less material and time are needed for tissue preparation. The quality of the tissue sections is increased, because artefacts caused by fixation and embedding processes are avoided. The perioplic horn is subdivided into the perioplic horny bulge and the glossy horn layer. The comparatively light (electron-permissible) perioplic horn is characterized by its relative lack of keratin filaments and keratin-filament-associated proteins which are only loosely linked by a few disulfide bonds. In the intercellular space, which is high in lipid content, drop-like electron-lucent dilations are observed. These formations reveal a high water binding capacity. The perioplic horny layer is very important for regulation of the water content, which was measured by physical methods. Compared to the horn produced in other regions of the hoof, the perioplic horn has the highest water binding as well as the fastest water uptake and water releasing capacity. The physiological water content was 48.0±6.86%, with a maximum of 71.36±1.84% and a minimum of 6.82±1.37%. In contrast, the adjacent coronary horn showed a water content of 18.74±0.62%, with a maximum of 27.27±1.46% and a minimum of 5.53±0.46%. Its high water content greatly influences the material properties of the perioplic horn. It is also important for the horn quality and for moisturising the outer coronary horn adjacent to the perioplic horny bulge. The perioplic horn shows only a limited mechanical resistance and barrier function against invasion of micro-organisms.