capsule

(KAP-sool) In medicine, a sac of tissue and blood vessels that surrounds an organ, joint, or tumor. A capsule is also a form for medicine that is taken by mouth. It usually has a shell made of gelatin with the medicine inside.

Carbohydrate coverings that have antigenic specificity, present on some types of bacteria and other micro-organisms. The capsule is usually composed of polysaccharides, polypeptides, or polysaccharide-protein complexes. These materials are arranged in a compact manner around the cell surface.