Histologic section through spinal meninges (Triple stain). Dura mater (D) is dense collagenous tissue. Arachnoid (A) consists of flattened fibrocytes attached to the deep surface of dura mater. Pia mater is composed of collagen fibers along the surface of white matter (W) and flattened fibrocytes lining the subarachnoid space (asterisk). Arachnoid trabeculae (arrows) connect pia mater and archnoid (the trabeculae appear thick because the subarachnoid space has collapsed).