When Tank, a 3-year-old male pit bull mix, arrived with his owner at a veterinary office in Humboldt County, his jaws packed with white powder, it was clear that something was seriously wrong. Earlier, Tank had mysteriously consumed an entire box of baking soda — odd behavior, even for an animal with famously indiscriminate eating habits. But more disturbing was Tank's demeanor. He sat trembling, his front legs stuck out at an awkward angle, his dilated eyes fixed on a distant point. A check of the heart revealed a coma-like 32 beats per minute, far below normal. Joseph Humble, the...