1. Definite morphological changes occur in the batonnets of the proximal convoluted tubule in stages of activity.
2. Atypical mitochondria but no batonnets exist in the regenerated cells found in chronic uranium nephritis.
3. No secretion of urea occurs in these cells which do not contain the cell organs.
4. The urea is secreted normally in the proximal convoluted tubule only (Leschke).
5. The urea appears in the form of granules, which are arranged in definite rows.
6. It is suggested that the secretion of the urea is by means of the mitochondrial batonnets which act as condensors.