feed rich in phosphates (wheat
bran, beans, peas, vetches, lentils, rape cake, cottonseed cake) or by a
privation of water, which entails a concentrated condition and high
density of the urine. Exposure in cold rain or snow storms, cold drafts
of air, and damp beds are liable to further disorder an already
overworked or irritable kidney. Finally, sprains of the back and loins
may cause bleeding from the kidneys or inflammation.

The right kidney, weighing 23-1/2 ounces, is shaped like a French bean,
and extends from the loins forward to beneath the heads of the last two
ribs. The left kidney (Pl. VIII) resembles a heart of cards, and extends
from the loins forward beneath the head of the last rib only. Each
consists of three distinct parts--(a) the external (cortical), or
vascular part, in which the blood vessels form elaborate capillary
networks within the dilated globular sacs which form the beginnings of
the secreting (uriniferous) tubes and on the surface of the sinuous,
secreting tubes leading from the sacs inward toward the second, or
medullary, part of the organ; (b) the internal (medullary) part, made
up in the main of blood vessels, lymphatics, and nerves extending
between the notch on the inner border of the kidney to and from the
outer vascular portion, in which the secretion of urine is almost
exclusively carried on; and (d) a large, saccular reservoir in the
center of the kidney, into which all uriniferous tubes pour their
secretions and from which the urine is carried away through a tube g
(ureter), which passes out of the notch at the inner border of the
kidney and which opens by a valve-closed orifice into the roof of the
bladder just in front of its neck. The bladder is a dilatable reservoir
for the retention of the urine until the discomfort of its presence
causes its voluntary discharge. It is kept closed by circular, muscular
fibers surrounding its neck or orifice, and is emptied by looped,
muscular fibers extending in all directions forward from the neck around
the blind anterior end of the sac. From the bladder the urine escapes
through a dilatable tube (urethra) which extends from the neck of the
bladder backward on the floor of the pelvis, and in the male through the
penis to its free end, where it opens through a pink, conical papilla.
In the mare the urethra is not more than an inch in length, and is
surrounded by the circular, muscular fibers closing the neck of the
bladder. Its opening may be