(mucous) coat, through which it finally opens. By this arrangement
in overfilling the bladder this opening is closed like a valve by the
pressure of the urine, and the return of liquid to the kidney is prevented.
The bladder (Pl. IX, fig. 2) is a dilatable, egg-shaped pouch, closed
behind by a strong ring of muscular fibers encircling its neck, and
enveloped by looped, muscular fibers extending on all sides around its body
and closed anterior end. Stimulated by the presence of urine, these last
contract and expel contents through the neck into the urethra. This last is
the tube leading backward along the floor of the pelvic bones and downward
through the penis. In the bull this canal of the urethra is remarkable for
its small caliber and for the S-shaped bend which it describes in the space
between the thighs and just above the scrotum. This bend is attributable to
the fact that the retractor muscles are attached to the penis at this
point, and in withdrawing that organ within its sheath they double it upon
itself. The small size of the canal and this S-shaped bend are serious
obstacles to the passing of a catheter to draw the urine, yet by extending
the penis out of its sheath the bend is effaced, and a small, gum-elastic
catheter, not more than one-fourth of an inch in diameter, may with care be
passed into the bladder. In the cow the urethra is very short, opening in
the median line on the floor of the vulva about 4 inches in front of its
external orifice. Even in her, however, the passing of a catheter is a
matter of no little difficulty, the opening of the urethra being very
narrow and encircled by the projecting membranous and rigid margins, and on
each side of the opening is a blind pouch (canal of Gaertner) into which the
catheter will almost invariably find its way. In both male and female,
therefore, the passing of a catheter is an operation which demands special
skill.

_General symptoms of urinary disorders._--These are not so prominent in
cattle as in horses, yet they are of a similar kind. There is a stiff or
straddling gait with the hind legs and some difficulty in turning or in
lying down and rising, the act causing a groan. The frequent passage of
urine in driblets, its continuous escape in drops, the sudden arrest of the
flow when in full stream, the rhythmic contraction of the muscles under the
anus without any flow resulting, the swelling of the sheath, the collection
of hard, gritty masses on the hair