What is serving to aid or help; serving as a chapel of ease; tributary. [R.] Not a city was without its cathedral, surrounded by its succursal churches, its monasteries, and convents. Milman called?

succursal — Serving to aid or help; serving as a chapel of ease; tributary. [R.] Not a city was without its cathedral, surrounded by its succursal churches, its monasteries, and convents. Milman. (Webster's 1913.)