Light micrograph of a renal cortex stained with the periodic acid Schiff (PAS) method. The PAS method allows distinction between the proximal convoluted tubules (most of the tubules seen here) and the distal convoluted tubules. Proximal convoluted tubules have a PAS positive brush border. Distal convoluted tubules have a broader lumen, lower epithelium and are devoid of a brush border. Here the distal tubules are sparse, but some can be seen in the vicinity of the glomerulus at the upper edge.