Dogs are what we call domesticated animals, meaning that for thousands of years they have played a very close and important part in men’s lives. One of the most valuable jobs a dog can be trained for is to act as a guide dog. These dogs are owned by blind people and lead the way when they want to go out. Such dogs are selected for this job when they are about two years, old, and it takes four or five months to train them. They are trained to lead their blind master down a street so that he won’t bump into other people or walk into building or lamp posts. They are also taught to stop at the curb and not lead their master across the road until the traffic has stopped or is a safe distance away. As they are highly intelligent animals, they can even help their masters safely in and out of buses and trains.