THE ABDOMEN. 



155 



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. 

 The Kidneys. The two kidneys lie on either side of 

 the vertebrae at the back of the abdominal cavity and 

 behind the peritoneum, between the last dorsal and 

 the third lumbar vertebrae, their inner edge being about 

 one inch from the spinous processes. They are bean- 

 shaped, four inches long, two inches wide, and one inch 



FIG. 58. Diagram of the relation of kidney to viscera, spine, and surface 

 points. (American Text- Book of Surgery.) 



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 ves- 

 sels 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 f 

 a substance made up of the straight uriniferous tubules 



