What did Paul discover about Himmelstoss when Himmelstoss joined them on the front lines?

He discovers that not only in Himmelstoss a coward, he's a bit crazy as well.

"When we run out again, although I am very excited, I suddenly think: "Where's Himmelstoss?" Quickly I jump back into the dug-out and find him with a small scratch lying in a corner pretending to be wounded. His face looks sullen. He is in a panic; he is new to it too. But it makes me mad that the young recruits should be out there and he here.

"Get out!" I spit.

He does not stir, his lips quiver, his moustache twitches.

"Out!" I repeat.

He draws up his legs, crouches back against the wall, and shows his teeth like a cur.

I seize him by the arm and try to pull him up. He barks.

That is too much for me. I grab him by the neck and shake him like a sack, his head jerks from side to side.

"You lump, will you get out--you hound, you skunk, sneak out of it, would you?" His eye becomes glassy, I knock his head against the wall--"You cow"--I kick him in the ribs--"You swine"--I push him toward the door and shove him out head first."