I have a Bulldog (75lbs & 5 years old) & a Yorkie (10lbs & he is 6 months). When I first got the yorkie, I was so worried because I thought that one of them would get hurt (my yorkie can take on my bulldog

). The vet told me that they are learning their place in the "pack". She said "what goes on between the dogs is between the dogs". My yorkie was quite the tough guy at first, but now they really love each other & get a long well. We just let them have at it & now it is over & they just play. I am sure this wouldn't work for everyone, but it worked for us!