Now , if every bridge has been traversed exactly once , it follows that , for each land mass ( except for the ones chosen for the start and finish ) , the number of bridges touching that land mass must be even ( half of them , in the particular traversal , will be traversed `` toward '' the landmass ; the other half , `` away '' from it ) .
If every bridge has been crossed exactly once , it follows that , for each land mass ( except for the ones chosen for the start and finish ) , the number of bridges touching that land mass must be even .