殼質,角素
Chitin \Chi"tin\, n. [See {Chiton}.] (Chem.) A white amorphous horny substance forming the harder part of the outer integument of insects, crustacea, and various other invertebrates; entomolin.
chitin n : a tough semitransparent horny substance; the principal component of the exoskeletons of arthropods and the cell walls of certain fungi