Cardiac muscle. Light micrograph of a transverse section through muscle tissue from a heart myocardium. The myocardium is the middle of the three layers of the heart wall, composed of a network of branching, elongated muscle cells (fibres, purple). Each cell possesses several nuclei (round, dark purple bodies), spaced out along its length and situated in the centre of the cell when seen in cross-section. The cell network is infiltrated by connective tissue (white) that is rich in capillary blood vessels. These supply the contracting muscle with oxygen and remove metabolic waste products. Trichrome blue stain. Magnification unknown.