THE EXCRETORY AND REPRODUCTIVE 



SYSTEMS. 



As explained in the last section, a portion of the waste 

 products produced by the activity of the cells of the 

 body is passed off through the lungs, but some other 

 outlet must be provided for the excretions that are not 

 in the form of gases. These liquid excretions, containing 

 various salts and urea, pass off through the kidneys and 

 the glands of the skin. 



The latter are of two kinds, sudoriparous or sweat 

 glands, and sebaceous or oil glands, with ducts opening into 

 the hair follicles near the surface. The sweat glands lie 

 deeper than the sebaceous glands. The former are sub- 

 cutaneous and consist of a more or less coiled tube with 

 a straight duct opening on the surface. They are most 

 abundant on the tip of the nose and the balls of the 

 feet. The sebaceous glands are very numerous all over 

 the body. Both are of microscopic size. 



A still more important part of the excretory system is 

 the urinary system, consisting of the kidneys, two ureters 

 leading from the kidneys to the bladder, the bladder, and 

 the urethra. 



The student should note that the kidney is not en- 

 veloped by the peritoneum, like the other abdominal 

 organs, but lies dorsad to it and is encased by a fibrous 

 covering known as the capsule. The hilus is that portion 

 of the concave surface where the renal artery and vein 

 and ureter enter. A median longitudinal section of the 

 kidney will show that the ureter within the kidney 



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