Jack Russells are an energetic breed that rely on a high level of exercise and stimulation. They are relatively free from any serious health complaints. Originating from dogs bred and used by the Reverend John Russell in the early 19th century, from whom the breed takes its name, the Jack Russell has similar origins to the modern Fox terrier. It has gone through several changes over the years, corresponding to different use and breed standards set by kennel clubs. Recognition by kennel clubs for the Jack Russell breed has been opposed by the breed's parent societies – which resulted in the breeding and recognition of the Parson Russell terrier. Jack Russells have appeared many times in film, television, and print – with several historical dogs of note.