North American beaver large, webbed hind feet. The unwebbed front paws are smaller, with claws. The eyes are covered by a nictitating membrane which allows the beaver to see under water. The nostrils and ears are sealed while submerged. A thick layer of fat under its skin insulates the beaver from its coldwater environment. The beaver's fur consists of long, coarse outer hairs and short, fine inner hairs (see Double coat). The fur has a range of colors, but usually is dark brown. Scent glands near the genitals secrete an oily substance known as castoreum, which the beaver uses to waterproof its fur.
Castor and Pollux branches. The standard Spartan oath was to swear "by the two gods" (in Doric Greek: νά τώ θεὼ, "ná tō theō", in the Dual number). The rite of "theoxenia" (θεοξενία), "god-entertaining", was particularly associated with Castor and Pollux. The two deities were summoned to a table laid with food, whether at individuals' own homes or in the public hearths or equivalent places controlled by states. They are sometimes shown arriving at a gallop over a food-laden table. Although such "table offerings" were a fairly common feature of Greek cult rituals, they were normally made in the shrines of the gods