Many invertebrates and some vertebrate animals, including amphibians, breathe through their skin—a process known as cutaneous respiration. Most of these animals are small, long, and flattened, like earthworms and flatworms. All animals that rely on their skin for respiration live in moist, damp places in order to keep their body surfaces moist. Capillaries (the small blood vessels) bring blood rich in carbon dioxide and deficient in oxygen to the skin’s surface, where gaseous exchange takes place by diffusion.