KSdan - agreed - the spine enters the front of the chest a little lower, and is just above 1/2 way up the body at the shoulder.
Also, I don't think the lungs are quite that large, with some gap just under the spine, and a little more forward at the rear side - particularly if the animal is full of food or water. Of course inhale or exhale, slight bend of the body, walking, standing, laying, etc, all cause changes.
i don't think the shoulder moves too much on an animal as it walks under it's own muscle power - feel your shoulder or your dog's shoulder as it moves about.
All I do know, is hits aren't always what they seem!