THE KIDNEYS 



175 



infections. Let them heal naturally or have a physician care 

 for them. When pimples become chronic, the condition is 

 called acne. If acne is 



ki dne;^ 



aortcc 



..venacccva 



wreter* 



treated in time, it can 

 be cleared up completely. 

 If not, it leaves scars 

 that are permanent. 

 Any unhygienic condition 

 of the body is likely to 

 affect the skin. In order 

 to keep the skin in good 

 condition, hygienic sug- 

 gestions concerning food, 

 water, rest, exercise, and 

 sunlight should be fol- 

 lowed. 



The kidneys. The or- 

 gans that excrete most of 

 the water and urea from the body are the kidneys. They lie in 

 the abdominal cavitv in the small of the back above the waist 

 line. They are bean-shaped with the concave side turned toward 

 the spine. The bulk of the kidney is made up of small coiled 



tubes, tubules, closely packed 



together and containing a large 



=^^f^^ number of blood vessels, and 



blacL^er 



The kidneys gather liquid wastes from the blood. 

 These materials are passed through the ureters to the 

 bladder and held in this reservoir ready for excretion. 



332 



i-r^/z/z^y 



m 



some nerves and lymphatics, 

 tubule of ^Water, urea, and organic salts 

 kx^-nc^^ pass by means of osmosis into 



The kidneys are made up of numerous minute ,i + U 1 TV* + Vw 1 



tubules. Their intimate relation with blood ves- ^''^^ tUDUieS. inCSC tUDUleS 

 sels makes possible the absorption of wastes. j^^^ j^^^ ^^,^ ^^^^^^ ^^^ 



from either kidney, the ureters, which are connected to a hollow 

 muscular sac called the bladder. The kidneys secrete urine which 

 passes down the ureters to the bladder. The bladder serves as a 



