Membrane

(měm'brăn.) [L. membrana.] (Anat.) A broad nervous and fibrous substance, which serves as a covering for different parts of the body, particularly the brain and the viscera. The membranes differ in thickne , according to the smallne of their fibres, or the number of their planes. These latter are termed lam inæ, and are distinguished into internal, external, and medial. Small portions of membranes, especially when they are very thin, are called pellicles; and some membranous lam inæ are united together by the intervention of a particular substance, composed of these pellicles, and called the cellular or spongy substance. [s. 591]