CHAPTER XIII. 



THE KIDNEYS AND THE EXCRETION OF URINE. 



THE Kidneys are two in number, and are situated deeply in the lum- 

 bar region of the abdomen, on either side of the spinal column, behind 

 the peritoneum. They correspond in position to the last two dorsal and 

 two upper lumbar vertebrae; the right being slightly lower than the left 

 in consequence of the position of the liver on the right side of the abdo- 

 men. They are characteristic in shape, about 4 inches long, 2% inches 

 broad, and 1-J- inch thick. The weight of each kidney is about 4| oz. 



FIG. 238. Plan of a longitudinal section through the pelvis and substance of the right kidney. U; 

 a, the cortical substance: 6, 6, broad part of the pyramids of Malpighii: c, c, the divisions of the pel- 

 vis named calyces, laid open; c'. one of those unopened; d, summit of the pyramids of papillae pro- 

 jecting into calyces: e, e, section of the narrow part of two pyramids near the calyces: p, pelvis or 

 enlarged divisions of the ureter within the kidney; it, the ureter; s, the sinus; h, the hilus. 



Structure of the Kidneys. The kidney is covered by a rather 

 tougk fibrous capsule, which is slightly attached by it's inner surface to 

 the proper substance of the organ by means of very fine fibres of areolar 

 tissue and minute blood-vessels. From the healthy kidney, therefore, it 

 may be easily torn off without injury to the subjacent cortical portion of 

 the organ. At the hilus or notch of the kidney, it becomes continuous 

 with the external coat of the upper and dilated part of the ureter (Fig. 

 238). 



