1. In plasma there exists a vasodilator substance specific for the vessels of the kidney.
2. This substance is a proteid of the albumin class and is precipitated by boiling and by alcohol.
3. It is present also in the serum.
4. It acts directly on the muscle coats of the arteries.
5. The process of clotting of the blood liberates a constrictor substance that acts on the renal vessels and also on the vessels of the limb.
6. This constrictor substance is not a proteid; it resists boiling, is soluble in alcohol, and acts directly on the muscle coat.