The urinary apparatus of the bird consists of two kidneys, from each of which a ureter extends and empties into the cloaca. =The Kidneys.= _Location._—The kidneys are located in excavations in the pelvic roof. They are related internally with the posterior aorta and vena cava, supero-internally with the lumbo-sacral vertebræ and superiorly and supero-externally with the ilium. The abdominal visceral organs lie below the kidneys. The kidneys are external to or above the peritoneum. _Shape._—In the fowl of average size the kidneys are 2½ inches long and are made up of three irregular lobes. The anterior lobe is usually the largest and the middle the smallest. The anterior border of the first lobe is located opposite the last true dorsal articulation. The anterior lobe is called the anterior pelvic or ilio-lumbar lobe, the middle the middle pelvic or ilio-sacral lobe, and the posterior the posterior pelvic lobe. _Structure._—The whole kidney has a fine transparent covering. The dark, brownish-red parenchyme can be seen through this membrane. It has a blood vascular system and a urinary tubular system. The larger arteries, the veins, and the nerves pass between the lobules, and the smaller vessels between the tubules. These form fine network or plexuses. The lymphatic vessels are very few, and are mainly found on the surface. The kidneys are pierced in their posterior third by the external iliac artery and at about its middle by the venous branches forming the posterior vena cava. The lobes are made up of _lobules_, which are plainly perceptible from the external surface. Each lobule is apparently a unit within itself. It receives its blood supply from small branches of the renal artery and is made up of a cortical or peripheral portion which contains the glomerules (Fig. 52, _A_) and a medullary portion, which is made up of tubules, or urinary canals, arteries, veins, and nerves. [Illustration: FIG. 50.—Photograph showing spinal cord and relative positions of the kidney, lung and heart. 1, Heart. 2, Lung. Note the indentations made by the ribs. 3, The anterior, middle and posterior lobes of the kidney. The lobules are plainly visible. 4, The lumbo-sacral segment of the spinal cord. 5, Terminal cord filament. 6, The cervico-dorsal segment of the spinal cord. 7, The brachial nerve plexus. 8 and 9, The lumbo-sacral plexus. 8, The ischiadic nerve. 9, The lumbar nerves. ]