skull is flat, while the King Charles' is domed. Finally, the muzzle length of the King Charles tends to be shorter than the typical muzzle on a Cavalier. The American Kennel Club has two classes, English Toy Spaniel (B/PC) (Blenheim and Prince Charles) and English Toy Spaniel (R/KC), while in the UK, the Kennel Club places the breed in a single class. Under the Fédération Cynologique Internationale groups, the King Charles is placed in the English Toy Spaniel section within the Companion and Toy Dog Group, along with the Cavalier King Charles Spaniel. Temperament The King Charles is a friendly breed, to the extent that it is not typically as suitable as a watchdog as some breeds, though it may still bark to warn its owners of an approaching visitor. It is not a high energy breed, and enjoys the company of family members, being primarily a lapdog. Although able to bond well with children and tolerant of them, it will not accept rough handling. It prefers not to be left alone for long periods. Known as one of the quietest toy breeds, it is suitable for apartment living. The breed can tolerate other pets well, although the King Charles still has the hunting instincts of its ancestors and may not always be friendly towards smaller animals. It is intelligent enough to be used for obedience work and, due to its stable temperament, it can be a successful therapy dog for hospitals and nursing homes. Health A natural bobtail can be found in some members of the breed, which is not a mutation of the T-box gene, and so is allowed under conformation show rules. Health-related research on the breed has been limited, with no major studies conducted in Britain. However, it has been included in studies outside the UK, including by the Orthopedic Foundation for Animals (OFA) in the United States. The King Charles Spaniel has a number of eye and respiratory system disorders common to brachycephalic dogs, and endocrine and metabolic diseases common to small breeds, as well as specific breed-associated health conditions. The average lifespan is 10 to 12 years, and the breed should be able to reproduce naturally. Eye and heart conditions The eye problems associated with the King Charles Spaniel include cataracts, corneal dystrophy, distichia, entropion, microphthalmia, optic disc drusen, and keratitis. Compared to other breeds, the King Charles Spaniel has an increased risk of