Household fights

Question
So heres the story. I have a 7 year old male westie that I've had since he was a puppy. I also have a 4 year old female mini daschund and 1.5 year old male jack russell. All are spayed/neutered. Recently, the westie and jack russell have been fighting, about what I have no clue. These aren't little fights either, but result in some pretty bad cuts. I get them seperated and leave them both alone until they cool down, usually for the rest of the day and over night. They aren't well trained and don't respond to commands once they get going. What can I do to prevent the fighting? Would it be best to find a new home for one of them?

Answer
It sounds as though the Jack Russell has reached the age of social maturity and is interested in displacing the Westie as head of the male household.  Or, the Westie is trying to convince him not to try.  Either way, the thing that concerns me is that they are drawing blood, which is not normal for simple tiffs about hierarchy.  In general, male dogs fight ritualistically, a holdover from the wild, where it would be a disadvantage to damage a hunting partner, but an advantage to at least convince him that your genes, not his, should be passed to the next generation.  One reason they think it's ok to do this is that you haven't any control over them.  Generally, the more control the human has, the less the dogs feel they need to assert themselves, although that isn't always the case.  By control, I don't mean punishment - I mean control of the dog's resources.  So, for example, if my dog will not "sit" and "stay" until her dinner bowl is placed on the floor, I simply take the dinner away for fifteen minutes.  If she still won't "sit"/"stay" (assuming she does understand the cue and has heard me), then the dinner goes away until tomorrow.  All my dogs, despite the fact that I am a trainer, go to puppy class at an early age, and continue through adulthood to be trained, and to be exposed to new dogs, situations, and people.  If you tried to mediate the fights in the beginning, it may be that they never settled the matter, and the fights continue.  But, now, you either need to separate them, re-home the younger dog (it isn't either fair, or easy, to try to find a new home for a seven year old dog), or hire a behaviorist to work with you to see if you can manage to keep both through training and behavior modification.  If you want to go that route, Animal Behavior Society and IAABC have listings on their sites.  
Good references for you:
"Aggression in Dogs" by Brenda Aloff (terrier person, too!)(available at Amazon, dogwise.com, and other retailers.
"Multiple Dogs" DVD by Trish King (available at Tawzer Dog Videos)