19. 1[ Enrolment of revenue agent. Every revenue- agent holding a certificate issued under section 18 may apply to be enrolled in any revenue- office mentioned therein and situate within the limits of the territory under the Chief Controlling Revenue- authority 2[ ; and, subject to such rules as the Chief Controlling Reveune- authority 2[ may, from time to time, make in this behalf, the officer presiding in such office shall enrol him accordingly, and thereupon he may practise as a revenue- agent in such office and in any revenue- office subordinate thereto.