Examples of such naturally occurring polymeric materials include, without limitation, (1) polysaccharides such as starch, cellulose, pectin, seaweed gums (such as agar, etc.), vegetable gums (such as arabic, etc.); (2) polypeptides; (3) hydrocarbons such as rubber and gutta percha (polyisoprene) and (4) regenerated materials such as cellophane or chitosan.