Peripheral nerve. Light micrograph of a cross section through an osmium-fixed peripheral nerve fascicle. A fascicle contains a bundle of nerve cells (fibres) and is surrounded by connective tissue called perineurium (pink, bottom right). The myelin around the axon of each nerve fibre is well preserved (black circles). Great variation in the sizes of the axons can be seen. This reflects the diversity of functions carried out by peripheral nerves. Endoneurium (delicate connective tissue) containing blood capillaries can be seen around the axons (pink). Van Giesen stained. Magnification x400 at 35mm size.