We have just purchase a Highland Terrier which is nearly 9 weeks old.
He is quite small and a bit of a runt of the litter but very lively. Since we
Bought him home his motions have been very loose and some seem to blood stained.
Yesterday his seemed to be straining and only passed blood and mucus.
Could you tell me what the problem is and if this is common in puppies.
He is having his first injection today at the vets.

Garrod, I am sorry I didn't see this earlier. I hope that you see this before you get to the vets office. Please take a sample of his stool with you when you take the puppy in for his appointment. It needs to be analyzed by the vet and should be part of your discussion with him/her. It could be that he simply needs a deworming, or it could be something else. The only way to know for sure what is going on is to work with your vet on this.

I think you need to take the dog to the vet urgently.