weird cat

We have a new cat he is probably about4 or 5 months. We found him and took him in. He is the best cat, but we also have a 9 month old lab (male) The cat will not fight back when Shadow puts the cats head in his mouth. Shadow doesn't hurt him but oreo gets soaking wet. Shadow is constantly pulling on oreo's tail. The cat loves Shadow because oreo will chase the dog and they go back in forth. My question is why won't Oreo be more aggressive with the dog. He will sometimes meow loud during this playing but never hiss or scratch.
Thanks Pam

My guess is that the cat has no problem with the dog doing this. He is just playing as if the dog were a sibling. However, I would also try and train the dog to ease up on the cat. Although they are just playing now, the dog is going to get MUCH bigger and may hurt the cat without meaning to. I had someone bring a cat in because the dog and cat were playing, the cat jumped up on something and the dog tried to stop her. He ended up breaking the cats back legs.