The smallest dogs are the Chihuahua, the Yorkshire Terrier and the Toy Poodle. A Yorkie once weighed in at only 283.5g. In Roman times and the Middle Ages, mastiffs wearing light armour, carrying spikes and pots of flaming sulphur and resin ran into battle against mounted knights. In World War II the Russians trained dogs to run suicide missions between the tracks of German tanks with mines strapped on their backs. Dogs' hearing is very acute.
Dogs naturally have a wonderful sense of smell.
They have many more sensory 'smelling' cells than a man's 5,000,000. Truffle hounds can find the fungus delicacy even when it's a foot underground. The average dog lives to around 15 years of age.