Although hard to imagine, dogs have long been used as research and testing subjects. In fact, in 1883, AAVS was founded specifically to protect dogs from being stolen or otherwise collected so they could be used as research tools, often suffering in agony with no analgesic or pain relief. Dogs are still used in research today. In 2012, 72,149 dogs were held in laboratories, with over 25,000 subjected to painful experiments.
Over a hundred years later, some dogs are still obtained from random sources, like Class B dealers or directly from pounds (a practice called pound seizure). In 2011, the National Institutes of Health announced that would start to phase out funding for research using dogs and cats obtained from random source Class B dealers. This policy came into full effect for dogs in October, 2014, and for cats in October 2012.
However, most dogs used in research are bred in laboratories to be either healthy or with a specific genetic deficit or by private companies that sell strictly to labs. The most common breed of dog used for experiments are beagles, but not because scientists view them as the best model for human disease. Rather, beagles are convenient to use because they are docile and small, allowing for more animals to be housed and cared for using less space and money.
Dogs are often used in biomedical research investigating heart and lung disease, cancer, aging, and orthopedics. They are still commonly used in toxicity studies to test the safety of human drugs and industrial chemicals, but are rarely used to assess the safety of personal care and household products. Additionally, some medical and veterinary schools use dogs in student training, particularly for surgery, despite the availability of alternatives that do not harm animals.