"Most people go to veterinary school because they love animals," says Colorado State University vet David Neil. "But then a very interesting transition takes place if you go into lab work"--which is what most research-minded veterinarians aspire to do rather than spend their professional lives flea-dipping the local Lassies and Garfields. It's a fundamental but subtle shift, Neil says, one that many vet students make before they realize they're doing so: "You go from someone who makes sick animals healthy to someone who makes healthy animals sick." At one point in his career, Neil found himself taking perfectly vital, eager young beagles and surgically giving them arterial blockages to replicate heart disease. Then he implanted pacemakers to study what forms of artificial heartbeats worked best on failing hearts. "They're so friendly; they love to be studied," Neil remembers, his voice dripping with melancholy. "As far as they're concerned, it's the highlight of their week." When the study was over, the dogs were euthanized.