[f. SPONGE sb.1 + -IN.] The horny or fibrous substance found in the skeleton of sponges: = KERATOSE sb.
1868. Watts, Dict. Chem., V. 404. Spongin, Städeler’s name for the organic matter of sponge.
1887. Sollas, in Encycl. Brit., XXII. 416. An axial fibre of organic matter,—probably of the same nature as spongiolin or spongin, the chief constituent of the fibres of horny sponges.
1888. Rolleston & Jackson, Anim. Life, 252. Lamellae of Keratin or Spongin, a substance near akin chemically to silk.
