수고 많으십니다.한가지 모르는게 생겼어요..
furthermore,the trans-siberian railway had not yet been built,which meant that chekhov had to make more than 2500 miles of his trip in a horse-drawn cart across frozen earth,an act of self-denial that subjected the young man in poor health to merciless suffering.

밑줄친 부분은 어느 동사에 걸리는 건가요?
해석이 잘 안되네요..어디에 걸쳐서 해야하는지..ㅜㅜ