Cilia in Different Segments of the Rat Nephron

We wish to report here the finding of single cilia in epithelial cells of the parietal layer of Bowman's capsule, of the proximal convoluted tubule, of the distal tubule, and of the collecting tubule of the rat kidney. Despite the observation by light microscopy, many years ago, of cilia in the tubules of rabbit and human kidneys (16), and despite many electron microscopic studies of kidneys in recent years, only one report of a cilium in a normal mammal ian kidney has appeared (5). The present observations of cilia in different parts of the nephron raise interesting questions concerning the significance of cilia in normal and neoplastic renal cells, from the standpoints of physiology, ontogeny, and phylogeny.