[Unusual structures in the epithelium of the mammary glands of white rats]

Ribbon-like structures derived from the rough endoplasmic reticulum have been revealed in the mammary gland epithelium at different physiological state. Some of these structures were located lying free in the background cytoplasm, while others penetrated cellular organelles and, sometimes, intracellular borders, passing from one cell into the cytoplasm of neighbouring cells. The genesis and functional significance of these structures is discussed.