Read it through once

I was not able to translate this to my satisfaction, but a professor helped me out. This was his explanation: The students in uniform belong to different college corps; not all students belong to corps; none join the corps except those who enjoy fighting. The corps students fight duels with swords every week, one corps challenging another corps to furnish a certain number of duellists for the occasion, and it is only on this battle-field that students of different corps exchange courtesies. In common life they do not drink with each other or speak. The above line now translates itself: There is truce during the Commers, war is laid aside, and fellowship takes its place.