Scared, possibly abused puppy

Question
I've just recently moved back into my parents place, and they have a new dog. They have had him for about a month and a half, and he's about 7 and a half months old. He's a border collie mix I'm pretty sure, and he has not been neutered. Since they've had him he's not been willing to be approached by anyone. I've been trying myself. I follow him around, but I don't chase him. I walk in his direction calmly and he keeps running around placing objects between him and myself. For example, we have a garden with a small fence around it. He will get on the other side of it and if I walk around it he will go to the opposite side. Eventually, either due to being tired or too scared he will stop somewhere long enough for me to get to him. It is very apparent how scared he is, and once I get close and start to pet him, he won't move. He won't sniff my hand when offered, he won't run off, and he won't take a toy to chew or even a treat. He won't run away again until I start to step away from him. I've been trying to get him leash trained, but once the leash is on him, he still refuses to budge. What I did today was walk out to the leashes range and called him to me a few times. When he didn't come to me, I would pull on the leash and drag him to me. I didn't have to pull REALLY hard, he would push away but take baby steps towards me to keep himself from hurting I guess. When I got him to me, I would give him some affection, petting him and such. After a little break and some love, I would repeat the process. We need him at least somewhat leash trained by Friday to take him to the vet. I would love some advice on how to get him though his skittish phase, and to get him leash trained properly without damaging his behavior even more than it is. Thanks much for your time!

Answer
You are doing the wrong things, quite innocently of course.  Never chase or drag a scared dog - imagine being dragged yourself toward an object you find terrorizing.  If you need to get him to the vet, please get a harness on him (he can wear it pretty constantly at first).  Any dog can slip out of a collar, no matter how tight, and you might very well lose him, so a harness is much safer.  For now, sit on the floor and toss treats to him (they should be large enough for him to see, but small enough that he can eat lots of them).  Real meat is best, as it tells the dog how very friendly and kind you are;-)  This dog is severely traumatized and this training takes time!  It's always better if you wait until the dog is willing to come up and sniff you, and you resist the temptation to reach for him. (The vet trip is a necessity, but you don't want to do that a lot.)  In the house, you can leave a leash drag (someone has to be there to supervise), and that way, you can pick up the end to take him for potty trips.  Get him to come with you by tempting him with some really cool food.  There are some good books that you can get to help you with this training, which can be very difficult and time consuming.  One is "The Cautious Canine" by Patricia McConnell.  I think that's a good one to start with.  Unfortunately, it sounds as though this poor pup missed being adequately socialized in puppy hood, which is a common cause for this behavior.  It isn't usually abusive contact that's the problem, but little to no contact with many people, that causes these issues.  Bless you for giving the little one a home.