Old dogs don't die; they can't. They've merely run up ahead; they're waiting for us just out of sight. Close your eyes late at night and you may smell his musky odor, or perhaps hear his snuffle from the next room. Pay attention and you may feel his nose on your hand or the back of your calf. When your final day comes, you can go on to meet him; he's never left you and never will, and when you close your eyes for the last time, you'll open them again to be met with his Bright eyes and wagging tail.
