Their leather is valuable, but their venom is even more highly prized, because it can save lives. India’s cobras and vipers used to be hunted and killed for their skin, but today the poisonous snakes are protected.   The Irulas, members of a low-status caste in southeastern India, used to earn a living selling hunted snakes until the practice was forbidden by law. Now they hunt the snakes for the Venom Extraction Center, which in turn supplies the entire country with anti-venom.