having once worn them, they must
not be left off until milder weather renders the change safe. The cheaper
articles of clothing are often dyed with lead or arsenic. Hence such
garments, like stockings and colored underclothing, worn next the skin
have been known to produce severe symptoms of poisoning. As a precaution,
all such articles should be carefully washed and thoroughly rinsed before
they are worn.

The Kidneys.

254. The Kidneys. The kidneys are two important organs in the
abdomen, one on each side of the spine. They are of a reddish-brown color,
and are enveloped by a transparent capsule made up of a fold of the
peritoneum. Embedded in fat, the kidneys lie between the upper lumbar
vertebrae, and the crest of the hip bone. The liver is above the right
kidney, and the spleen above the left, while both lie close against the
rear wall of the abdomen, with the intestines in front of them. The human
kidneys, though somewhat larger, are exactly of the same shape, color, and
general appearance as those of the sheep, so commonly seen in the markets.

The kidneys are about four inches long, two inches across, one inch thick,
and weigh from 41/2 to 51/2 ounces each. The hollow or concave side of the
kidneys is turned inwards, and the deep fissure of this side, known as the
hilus, widens out to form the pelvis. Through the hilus the
renal artery passes into each kidney, and from each hilus passes outwards
the renal vein, a branch of the inferior vena cava.

A tube, called the ureter, passes out from the concave border of each
kidney, turns downwards, and enters the bladder in the basin of the
pelvis. This tube is from 12 to 14 inches long, about as large as a goose
quill, and conveys the secretion of the kidneys to the bladder.

255. Structure of the Kidneys. The pelvis is surrounded by
reddish cones, about twelve in number, projecting into it, called the
pyramids of Malpighi. The apices of these cones, known as the
_papillae_, are crowded with minute openings, the mouths of the
uriniferous tubules, which form the substance of the kidney. These
lie parallel in the medullary or central structure, but On reaching the
cortical or outer layer, they wind about and interlace, ending, at last,
in dilated closed sacs called Malpighian capsules.

[Illustration: Fig. 108.--Vertical Section of the Kidney.

A, pyramids of Malpighi;
B, apices, or papillae, of the pyramids, surrounded by subdivisions of
the pelv