. "pared by the hydrolysis of poly(vinyl acetate)); or By dissolution or chemical treatment of natural organic polymers (for example, cellulose) to produce polymers such as cuprammonium rayon (cupro) or viscose rayon, or by chemical modification of natural organic polymers (for example, cellulose, casein and other proteins, or alginic acid), to produce polymers such as cellulose acetate or alginates." . . . .