Some time ago, visting a less blessed part of my community I came across a very badly treated Pavement Special. After seeing what the dog was being put through, I took him home and began teaching to trust people again. A few years on, he has improved significantly. He is lovealbe and even allows strangers to touch him. But he is very lonely. He is a large breed dog and we have tried to introduce a small breed to the house but he didn't react well, in fact, I think he wa trying to kill it. What I want to know is, what breed of dog would make a suitable friend? And is there some guideline I should follow introducing the two?