Veterinary medicine is concerned with the health and treatment of animals. Experiments and surgery on animals have been used for centuries to train doctors, but now veterinary medicine is a highly specialized science in its own right. The training is similar to that for doctors, but is in some ways more complicated, because of the many different animals which must be studied. The veterinary surgeon must be highly skilled at making a diagnosis because, unlike humans, animals cannot help by describing how they feel Veterinary medicine can be divided into two groups Small animal veterinary medicine is concerned with the health and treatment of domestic animals such as cats, dogs and other small pets. A large animal veterinary practice looks after farm livestock and horses, and is generally concerned with preventing illness in these animals, as much as treating them once they are sick. Veterinary surgeons routinely treat farm livestock to remove worms and other parasites which slow their growth or reduce milk production. Vaccines are available to prevent many diseases of domestic pets and farm livestock, by immunizing them against common diseases