It is principally white-bodied and smooth, rough or broken-coated and can be any colour. 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. Her colouring was described as '...white, with just a patch of dark tan over each eye and ear; whilst a similar dot, not larger than a penny piece, marks the root of the tail.' Davies, a friend of Russell's, wrote: 'Trump was such an animal as Russell had only seen in his dreams'. She was the basis for a breeding program to develop a terrier with high stamina for the hunt as well as the courage and formation to chase out foxes that had gone to ground.