Page:Structure and functions of the body; a hand-book of anatomy and physiology for nurses and others desiring a practical knowledge of the subject (IA structurefunctio00fiskrich).pdf/161

 the muscular system. So probably they secrete into the blood minute quantities of a substance or substances beneficial to the body, especially to the muscular system.

—Diagram of the relation of kidney to viscera, spine, and surface points. (American Text-Book of Surgery.)

The Kidneys.—The two kidneys lie on either side of the vertebræ at the back of the abdominal cavity and behind the peritoneum, between the last dorsal and the third lumbar vertebræ, their inner edge being about one inch from the spinous processes. They are bean-shaped, four inches long, two inches wide, and one inch thick, and are embedded in a mass of fat and loose areolar tissue. They can be felt only when misplaced or when enlarged, as by tuberculosis or malignant disease.

The whole kidney is enveloped in a fibrous capsule which normally may be peeled off but which in some diseases becomes adherent. On the internal border is a fissure or hilum, through which pass the blood vessels and the ureter. Upon entering, the ureter dilates into a sac, the pelvis of the kidney, into which project the Malpighian pyramids of the medullary substance, a substance made up of the straight uriniferous tubules