1. The inconstant results of past observations on the relation of pituitary extracts to renal activity have been due chiefly to unsuitable methods.
2. A standard curve of artificially induced polyuria may be plotted for rabbits, giving 200 cc. of water by mouth.
3. Extracts of the pars intermedia and posterior lobe of the hypophysis, given by mouth, subcutaneously, or intravenously, are able definitely to check polyuria thus induced. Extracts of the anterior lobe show a similar effect, but only to a slight degree.
4. This antidiuretic effect is constant, and is independent of (a) changes in blood pressure, (b) intestinal absorption, and (c) the vagi. The effect is apparently prevented or delayed by division of the splanchnics, and is diminished by division of the renal nerves near the hilus.
5. A similar antidiuretic property is possessed: (a) by ß-imidazolylethylamine, (b) by p-oxyphenylethylamine, (c) by a preparation from Secale cornutum, (d) by small doses of nicotine, (e) by large doses of caffeine, and (f) by extracts of the adrenal cortex.
6. No effect on the polyuria is produced: (a) by strychnine (b) by morphine, (c) by adrenalin, or by extracts of (d) thyroid, (e) thymus, (f) pineal, (g) pancreas, or (h) corpora lutea.
7. In animals under chloral or paraldehyde anesthesia a short and inconstant initial increase in flow of urine is seen.
8. The antidiuretic effect is absent or only slightly marked in checking the so called salt diuresis.