One disadvantage of string dogs is that the string is a hybrid product, so the future appearance and size will be uncontrollable. The second disadvantage of stringing dogs is that different strings will have different diseases. The following are some typical diseases that will occur. Gene mutation can cause diseases, ptosis and ectropion of lower eyelid can cause paralytic ectropion, ectropion can lead to long-term infection and inflammation of eyes, and long ears can lead to bacterial infection of ear canal. Dogs belong to Chordata, Vertebrate, Mammalian, Orthoptera, Carnivora, Schipoda and Canidae. Chinese is also called "dog", and dogs are distributed all over the world. Dogs, horses, cows, sheep, pigs and chickens are also called "six animals". Some scientists believe that dogs were domesticated by early humans from the gray wolf, and the domestication time was from 40,000 years ago to 1.5 million years ago. Known as "the most loyal friend of mankind", it is the pet with the highest reproductive rate, and its life span is about 12~ 18 years. In China culture, dogs belong to one of the 12 Zodiacs, ranking 1 1 among the 12 Zodiacs.