The title of a treatise written in the reign of Edward III. containing the writs which were then most in use, annexing to each a short comment concerning their nature and the application of them, with their various properties and effects. 3 Reeve, Eng. Law, 152. It is so called by way of distinction from the New Natura Brevium of Fitzherbert, and is generally cited as “O. N. B.,” or as “Vet Na. B.” using the abbreviated form of the Latin title.