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.
Nobel Prize in Physiology or Medicine this year's prize 'for Physiology or Medicine' to three men who had until recently been regarded as 'mere animal watchers'". Laureates have been awarded the Nobel Prize in a wide range of fields that relate to physiology or medicine. , eight Prizes have been awarded for contributions in the field of signal transduction through G proteins and second messengers. 13 have been awarded for contributions in the field of neurobiology and 13 have been awarded for contributions in Intermediary metabolism. The 100 Nobel Prizes in Physiology or Medicine have been awarded to 195 individuals through 2009. Twelve women have received