THE URINARY APPARATUS 333 



of ignorant breakers, who continue to adopt the same unnecessary practice. 

 As matter of fact they produce little if any inconvenience, and usually 

 disappear between two and three years old, when the first and second 

 temporary grinders are shed. 



3. THE URINARY APPARATUS 



From an anatomical point of view, 

 two kidneys with their ducts, named 

 the ureters, which open into a mus- 

 culo-membranous sac, the bladder, and 

 this again has a tube, short in the 

 female, of considerable length in the 

 male, by which the fluid collected in 

 the bladder is discharged from the 

 body at convenient intervals, and is 

 named the urethra. In the male this 

 tube terminates at the extremity of 

 the penis, which it traverses along its 

 whole length. From a physiological 

 stand-point, the kidneys are organs by 

 which the excess of water, as well as 

 the salts and the nitrogen of the body, 

 are got rid of, the latter substance 

 being chiefly in the form of urea, of 

 uric and hippuric acids, and crea- 

 tinine, which represent the waste of 

 the proteids or albuminous and albu- 

 minoid components of the tissues. 



The Kidneys (fig. 131) are two 



in number, one being situated on each 

 side of the lumbar vertebrae, partly 

 under cover of the last ribs, and rest- 

 ing against the under surface of the 

 loins, where they are embedded in much 

 fat. The right kidney is somewhat 

 heart-shaped and rather the larger of 

 the two. It reaches to the level of the 

 16th rib and touches the liver in front 



the urinary apparatus consists of 



Fig. 131. — The Kidneys, Ureters, and Bladde 



rk, Right kidney. L K, Left kidney, a, Right 

 ureter. B, Abdominal aorta, c, D, E, F, I, Arteries 

 arising from the same. G, Bladder. H, Pelvis. 



it weighs about 27 oz. The left 



