Gouged these chasms round their fretted sockets?
Ever from their hair and through their hands' palms
Misery swelters.  Surely we have perished
Sleeping, and walk hell; but who these hellish?
-- These are men whose minds the Dead have ravished.
Memory fingers in their hair of murders,
Multitudinous murders they once witnessed.
Wading sloughs of flesh these helpless wander,
Treading blood from lungs that had loved laughter.
Always they must see these things and hear them,
Batter of guns and shatter of flying muscles,
Carnage incomparable, and human squander
Rucked too thick for these men's extrication.
Therefore still their eyeballs shrink tormented
Back into their brains, because on their sense
Sunlight seems a blood-smear; night comes blood-black;
This emphasises the point that these soldiers are trapped and tortured in a mental cage and there is no possible way to free themselves.  The verb ‘rucked’ is unexpected, referring usually to fabric that is gathered and creased.