The border traverses a variety of terrains, ranging from major urban areas to uninhabitable deserts. Approximately 350 million legal crossings occur annually, and is the most frequently crossed border in the world. The total length of the continental border is 1,954 miles (3,145 km).
Only a veterinarian will know what's wrong with your dog but usually stumbling, wobbling and falling down is associated with neurological problems, especially if there aren't any other signs. I would really take him to the vet as soon as you can.
Why Horses Stumble. Stumbling can be caused by a number of things, including long toes, hoof imbalance, laziness or boredom, or a number of serious medical conditions. Some horses stumble or stub their front toes frequently, with the toe hitting the ground while the knee is still bent and the leg collapses instead of taking weight.