C.S. Lewis's Lost Aeneid -- "as when Achilles bound him..."

"in somnis, ecce, ante oculos maestissimus Hector
uisus adesse mihi largosque effundere fletus,
raptatus bigis ut quondam, aterque cruento
puluere perque pedes traiectus lora tumentis. "

"Lo, in a dream great Hector at my bedside stood,
Never before so sorrowful; in grime and blood,
As when Achilles bound him to his car and drew
The corpse, with sinews swollen where the thong pierced through."

(Lewis Translation)

In class we struggled with the last line:

"perque pedes traeiectus lora tumentis"

for some reason the concept was unclear and we really just glossed over it. That the "lora" ("thong") was what bound him to Achilles' chariot makes so much more sense! We seemed to just throw it in to the sentence, like he had pierced feet but not that they were used to tie him to the chariot, they had no real purpose in the sentence.