THE EXCRETORY AND REPRODUCTIVE 

 SYSTEM. 



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 subcutaneous 

 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 enveloped 

 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 sur- 

 face where the renal artery and vein and ureter enter. A 

 median longitudinal section of the kidney will show that 

 the ureter within the kidney enlarges, forming the pelvis, 

 into which projects the renal papilla (Fig. 87). This is 

 better demonstrated in a transverse section. 



164 



