This small Terrier, which receives its name from its creator, Parson Jack Russell, from Devon, England, emerged in the early XIX century for fox hunting, carried horseback with its owner. The small worker Jack Russell was also popular as a show dog, having participated in the first, 1862, English show. 
Active and alert, the Jack Russell Terrier is a medium sized working Terrier with evident strength and resistance. It stands between 30 and 35 cm. The head should be well balanced, with a moderate width, narrowing towards the eyes, not prominent cheekbones. The eyes are almond shaped, small, not bulgy, dark colored. The ears are small, “V” shaped, moderate thickness, button; the nose should be completely black (not brown, or white or liver). The neck is clean and with enough length to balance the dog; the shoulders, long and sloped, the chest, narrow and moderate in depth; the back, strong and straight; the tail, moderately high inserted, strong, with happy movement, carried not over the back or curled, or like a squirrel. The forelegs are strong and straight; the hindquarters, softly modeled with more angulations. The coat should be short or hard; the short hair is straight but strong; the hard hair is double coated, with a thick undercoat, and with hard external hair. The color should be completely white, or predominantly white with tan patches, lemon or black, or a combination of any of these colors, preferably in the area of the head and/or tail. Ideal size; for males 35 cm and for females 33 cm. During an undetermined period of time, the FCI admits 26 cm specimens (males and females) for breeding as well as beauty shows.
Strong and adaptable, the Jack Russell Terrier is happy as a family dog, which gets along with children and adults alike. It is not a biter r hyper nervous, although it needs a steady hand to comply with the house rules. Quick as a lightning, the Jack Russell is a work dog with plenty of energy, without bad habits, who loves people, horses and other dogs (although some specimens can be aggressive with other dominant dogs). It digs naturally, it is very curious and can tend to wander. Those who live in the city should be very careful with traffic, since these little devils can disappear in a heartbeat, without lifting its head if following a trail.
The wire hair Jack Russell has external wire hair and thick undercoat. As well as short haired, it is a robust, individualist dog, with a lot of brain.
The Jack Russell puppy should be happy and vigorous. Avoid hair excess, bad bite, twisted legs and raised ears if you intend to display it at a show. 
A Jack Russell should weigh approximately 1.5 kg after the seventh or eighth week. It reaches its maximum height at about the year, although physical and mental maturity is not reached before 18 or more months. The buyer should select a healthy looking puppy, cheerful and balanced, with a good structure according to the breed’s standard. Those that are too bold, or too timid should be avoided. Atypical characteristics that should be avoided are raised ears, twisted limbs, incorrect bites and excessive coats. Adolescence is marked by the emerging of the dog’s true character. In general the temperament should not change, but due education and socialization should be patent in the youngster’s growth. Straight coats often develop moustaches in this period, and the coat color can lighten, mostly the black in the tricolors.
Training the Jack Russell puppy is a full time commitment. The only thing a Jack Russell is faster than running is thinking! You will have to raise early a lot to get ahead of a Jack Russell.
The Jack Russell in general is a very resistant, healthy and well done breed. It doesn’t need a special diet, although it is recommendable to follow a program indicated by the breeder. Demands as for exercise and training are high to keep this little hunter happy and healthy. Due to the fact that breeders have concentrated in keeping the Terrier functionality and strong instinct, the Jack Russell is kept relatively natural and doesn’t have serious hereditary problems. Breeders inform retinal luxation and hereditary cataracts as two problems that can emerge, but mostly in non registered lunes in the Origin Website of the KC. The buyer is advised to ask for the eye certificate from the breeder. In some lines kneecap luxation and myasthenia gravis (which affects the muscles) have been registered. The Jack Russell lives from 12 to 14 years and more.
The puppy stage is like life: too short… take your time to smell the roses.