What passing-bells for these who die as cattle?
Only the monstrous anger of the guns.
Only the stuttering rifles' rapid rattle
Can patter out their hasty orisons.
No mockeries now for them; no prayers nor bells,
Nor any voice of mourning save the choirs,--
The shrill, demented choirs of wailing shells;
And bugles calling for them from sad shires.
What candles may be held to speed them all?
Not in the hands of boys, but in their eyes
The ‘wailing shells’ are  personified  as ‘demented choirs’, demented meaning insane and out of control. 
 Note the  consonantly rhyming   ‘shrill’ and ‘shells’ mimic the sound of the guns. 
