[Light and electron microscopic and histochemical studies on the cloaca epithelium of the domestic hen]

The mucous membrane of the Cloaca was investigated light and electronmicroscopically in 20 hens. Some histochemical investigations and a reabsorption test were carried out. The surface of the Coprodaeum is being formed by villi and deep crypts. The former disappears gradually within the Urodaeum. The latter crypts can be found down to the Proctodaeum. The epithelium of the Coprodaeum and Urodaeum consists of goblet cells and highprismatic cells containing secretory granules. The Proctodaeum can be subdivided into three parts. A cranial, containing the same epithelium as the Coprodaeum, a middle with a two layered highprismatic epithelium and a caudal part with a multilayered squamours epithelium. The columnar cells of all parts of the cloaca show a strong reaction to acid phosphatase and ATPase, whereas alkaline phosphatase is almost negative.