12 year old Jack getting meanier

by p. garcia
(california)

I have a 12 year old Jack Russell and a 7 year old Lab. We rescued a cocker spaniel/ lab mix last year; who was 3 months old. The dogs took to the puppy at first, after the cocker spaniel got about 5 months old, we noticed our Jack Russell becoming very aggressive toward him. The puppy was fixed but the aggression is still present. During meal times, when our son plays with the newer dog, actually anytime. The fighting is very serious and vicious. The smaller dog has been bitten badly on more than one occasion. I do not want to get rid of our Ringo but it's becoming very difficult. Please send some advise on how to save my extended family.