On the functional morphology of the large intestinal mucosa of the ox (Bosprimigenius f. taurus), sheep (Ovis ammon f. aries) and goat (Capra aegagrus f. hircus)

The mucous membrane of the large intestine of the ox, sheep and goat was st udied using light and electron microscopy. The surface epithelium possesses the well-known complement of organelles with a conspicuous number of mitoc hondria as a source of energy for absorptive activities. Occasionally, brus h cells are found in the epithelium; the functional significance of this ty pe of cell is still under discussion. In the present material, electron-luc id spheroids (diameter: 45 x 35 nm), which tend to fuse, appear in the supr anuclearly located osmiophilic granules. The structure and appearance of th e epithelium cells in the crypts of these species correspond to previous de scriptions in other mammals. In the epithelial cells of the deep glandular region, dense accumulations of mainly rounded granules (diameter up to 400 nm) are found apically in the cytoplasm. Their functional significance is s till under discussion. Acid phosphatase activity, as a marker enzyme for ly sosomes, points to degenerative processes in connection with the physiologi cal death of enterocytes. In contrast, the negative alkaline phosphatase re action indicates that, according to our findings, the epithelial transport of substances in the large intestine of ruminants - in principle contrary t o the situation in the small intestinal enterocytes - occurs without the ai d of this enzyme. The demonstrated ATPase activity on the other hand, is re lated to a primary active ion transport linked with membrane exchange of no n-electrolytes in connection with transepithelial events of absorption and secretion in the large intestine.