Who says you can’t teach an old dog new tricks? That’s turning out not to be true at our house. My 15 ½ year old dog, Darla, so sharp, she’s taught herself. Do I sound pleased? Because I’m not. This trick involves the cat. Darla has lived every day of her life with a cat. She’s never shown any interest in the dry cat food I leave down for the diva, I mean, the cat. A couple weeks ago, something