THE EXCRETORY AND REPRODUCTIVE 
SrolEM, 
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, sudortparous 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 /iulus 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. 
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