The =kidneys= are smooth and bean-shaped; they are more flattened
dorso-ventrally, more elongated, and smaller at the extremities than
those of the dog. The length is about twice the width. They are usually
almost symmetrically placed on either side of the first four lumbar
vertebræ. (Variations in position are not rare, and involve the left
kidney oftener than the right. The former has been found near the pelvic
inlet.) The external border lies against the flank parallel with the
edge of the longissimus muscle. The posterior extremity usually lies
about midway between the last rib and the external angle of the ilium.
The anterior extremity of the right kidney usually extends as far
forward as the last rib, but has no contact with the liver.
The weight of the kidney of a medium-sized pig is about seven to nine
ounces (200 to 250 grams). The ratio of their combined weight to that of
the body is about 1 ∶ 150–200.
=Structure.=—The hilus is about in the middle of the inner border. The
pelvis is funnel-shaped, and divides into two calyces majores, which
pass in a curve forward and backward respectively, and give off some
eight to twelve short calyces minores; each of the latter contains a
papilla. Some papillæ are narrow and conical, and correspond to a single
pyramid; others are wide and flattened, and result from the fusion of
two or more pyramids; some project directly through the wall of the
pelvis without the formation of a calyx. The renal pyramids are
distinct, but it is apparent that some are compound, _i. e._, formed by
fusion of primitively separate pyramids. The renal artery enters the
ventral part of the hilus, and the ureter leaves it dorsally.
The only special feature in regard to the =ureter= is that it is at
first relatively wide and gradually diminishes in caliber.
The =bladder= is relatively very large; when full, it lies chiefly in
the abdominal cavity. It is almost completely covered with peritoneum.