-> Geez, I just got a couple of .jpg's in email showing a pit bull that had been
-> so incautious as to take on a porcupine. His face is entirely occluded by
-> spines.  Maybe he'll be a little more polite, next time.

Doubtful.
Pit Bull's appear to be virtually immune to pain under most
circumstances.

My own stood there being shredded by a feral cat until I
drove it off.

Attacked viciously by a very nasty Pit Bull and seriously injured
my dog appeared unaffected in demeanor. 

These dogs raised to be mean can and will continue to fight even after
mortally wounded.
                 
OTOH my friend when stepping on a sand spur will lift his foot and wait
for me to extract it, go figure.
--- Platinum Xpress/Win/WINServer v3.0pr5