Whose work first described the chitin exoskeleton of insects and arachnids?

As microscopy improved in the 19th century, scientists began to understand why insects and arachnids have such tough outer coverings. Comparative anatomists identified chitin as a key component of the arthropod exoskeleton. This discovery explained how these animals support their bodies, protect themselves, and molt as they grow. Chitin later became important in biology, materials science, and medicine. It remains one of the defining molecules of insects, spiders, crustaceans, and related groups.