1, 1, 1. Section of the collecting tubes, showing their diameter, their cavity, and their lining epithelium. 2, 2. Ditto of the ascending portion of the urinife-rous tubules. 3, 3, 3. Section of the descending branch of the same, showing their much smaller calibre, slightly larger cavity, and very flat epithelium. 4, 4, 4. Section of the blood vessels.
