In 1758, the Swedish botanist and zoologist Carl Linnaeus published in his Systema Naturae the binomial nomenclature – or the two-word naming – of species. Canis is the Latin word meaning "dog", and under this genus he listed the dog-like carnivores including domestic dogs, wolves, and jackals. He classified the domestic dog as Canis familiaris, and on the next page he classified the wolf as Canis lupus. Linnaeus considered the dog to be a separate species from the wolf because of its cauda recurvata - its upturning tail which is not found in any other canid.
In a study of seven breeds of dogs (Bernese mountain dog, basset hound, Cairn terrier, Epagneul Breton, German Shepherd dog, Leonberger, and West Highland white terrier) it was found that inbreeding decreases litter size and survival. Another analysis of data on 42,855 dachshund litters found that as the inbreeding coefficient increased, litter size decreased and the percentage of stillborn puppies increased, thus indicating inbreeding depression. In a study of boxer litters, 22% of puppies died before reaching 7 weeks of age. Stillbirth was the most frequent cause of death, followed by infection. Mortality due to infection increased significantly with increases in inbreeding.
Human emigrants from Siberia that came across the Bering land bridge into North America likely had dogs in their company. Although one writer even suggests that the use of sled dogs may have been critical to the success of the waves that entered North America roughly 12,000 years ago, the earliest archaeological evidence of dog-like canids in North America dates from about 9,400 years ago.:104 Dogs were an important part of life for the Athabascan population in North America, and were their only domesticated animal. Dogs as pack animals may have contributed migration of the Apache and Navajo tribes 1,400 years ago. This use of dogs in these cultures often persisted after the introduction of the horse to North America.
A Colorado study found bites in children were less severe than bites in adults. The incidence of dog bites in the US is 12.9 per 10,000 inhabitants, but for boys aged 5 to 9, the incidence rate is 60.7 per 10,000. Moreover, children have a much higher chance to be bitten in the face or neck. Sharp claws with powerful muscles behind them can lacerate flesh in a scratch that can lead to serious infections.
The practice of using dogs and other animals as a part of therapy dates back to the late 18th century, when animals were introduced into mental institutions to help socialize patients with mental disorders. Animal-assisted intervention research has shown that animal-assisted therapy with a dog can increase social behaviors, such as smiling and laughing, among people with Alzheimer's disease. One study demonstrated that children with ADHD and conduct disorders who participated in an education program with dogs and other animals showed increased attendance, increased knowledge and skill objectives, and decreased antisocial and violent behavior compared with those who were not in an animal-assisted program.
Clip the dog's nails. If left untrimmed, a dog's nails can curl under into the paw pads or twist toes in a way that causes joint damage. To keep your dog's nails short, clip them regularly, depending on how fast his nails grow. If you can hear his nails on the ground when he walks, that means his nails are touching the ground, and are too long. 
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